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LOUIS   PASTEUR 

(1822-1895) 

(From  a  bronze  by  Theodore  Riviere.) 


PASTEUR 

THE  HISTORY  OF  A  MIND 


BY 

EMILE  DUCLAUX 

Late  Member  of  the  Institute  of  France 

Professor  at  the  Sorbonne  and  Director 

of  the  Pasteur  Institute 


TRANSLATED  BY 


ERWIN  F.  SMITH  and  FLORENCE  HEDGES 

Pathologists  of  the  U.  S.  Department  of  Agriculture 


ILLUSTRATED 


PHILADELPHIA  AND  LONDON 

W.  B.  SAUNDERS  COMPANY 

1920 


Copyright,  1920,  by  W.  B.  Saunders  Company 


"ft  551 -TIG 
J)  152. 


PRINTED     IN    AMERICA 


CONTENTS 


Introduction v 

Author's  Preface xxxi 


FIRST  PART 
WORKS  ON  CRYSTALLOGRAPHY 

Chaptbb  Page 

I.  The  Predecessors  op  Pasteur:  Haut,  Weiss,  Delafosse  1 

II.    BlOT  AND  J.  HERSCHEL 7 

III.  Pasteur:  The  Tartrates 12 

IV.  The  Paratartrates 16 

V.  Aspartates  and  Malates .    .    .    .  20 

VI.   Molecular  Dissymmetry 23 

VII .  Dissymmetry  op  Cellular  Life 28 

VIII.  Substances  Inactive  Through  Loss  of  Dissymmetry    .    .  32 

IX.  Combinations  Between  Acitve  Molecules 39 

X.   Means    of   Separating   the   Right-   and  Left-handed 

Substances 43 

XI.  General  Conclusions 46 


SECOND  PART 
LACTIC  AND  ALCOHOLIC  FERMENTATIONS 

I.  The  Knowledge  of  Fermentations  before  Lavoisier  .   .  51 

II.  From  Lavoisier  to  Gay-Lussac 56 

III.  Cagniard-Latour,  Schwann,  Helmholtz 59 

IV.  Liebig 64 

V.  Pasteur:  Lactic  Fermentation 67 

VI.  Alcoholic  Fermentation 73 

VII .  Aerobic  Life  and  Anaerobic  Life 79 


11  CONTENTS 

THIRD  PART 
SPONTANEOUS  GENERATIONS 

Chapter  Page 

I.  Spontaneous  Generation  and  Fermentation 85 

II.  Buffon,    Needham,    Spallanzani,    Schultze,    Schwann, 

SCHROEDER  AND  DuSCH 87 

III.  Pouchet,  Pasteur:  The  Germs  op  the  Air 91 

IV.  In  the  Air  There  are  Living  Germs 95 

V.  Response  to  the  Arguments  in  Favor  op  Spontaneous 

Generations 100 

VI.   Distrd3ution  op  Germs  in  the  Air 101 

VII .  Discussion  with  Pouchet 104 

VIII.  Discussion  with  Frémy Ill 

IX.  Discussion  with  Bastian 114 

FOURTH  PART 

WINES  AND  VINEGARS 

I.  Industrial  Methods  in  the  Manufacture  op  Vinegar    .  121 

II.  The  Mycoderma  op  Vinegar 124 

III .  Discussion  with  Liebig 128 

IV.  The  Diseases  op  Wine 133 

V.  Action  op  Oxygen  on  Wine 136 

VI.  The  Heating  op  Wines 141 

FIFTH  PART 

STUDIES  ON  THE  DISEASES  OF  SILKWORMS 

I.  Orientation  toward  Pathology 145 

II.  The  Corpuscular  Disease  (Pebrine) 149 

III.  Studies  op  1865 154 

IV.  Studies  of  1866 158 

V.  Is  the  Corpuscle  the  Cause  op  the  Disease? 162 

VI.  Studies  of  1867 168 

VII.  The  Disease  op  the  Morts-Flats  (Flacherie) 173 

VIII.  Studies  op  1868,  1869,  1870 178 

SIXTH  PART 

STUDIES  ON  BEER 

I.  Studies  on  Brewing 187 

II .  Transformation  of  One  Species  into  Another 190 

III.  Anaerobic  Life  op  Aerobic  Species 198 


CONTENTS  111 

Chapter  Page 

IV.  Aerobic  Life  of  Anaerobic  Species 202 

V .   Ideas  of  Claude  Bernard  on  Fermentation 206 

VI.  Discussion  of  the  Ideas  of  Claude  Bernard 210 

VII.   Origin  of  the  Yeasts  of  Wine 214 

SEVENTH  PART 

STUDIES  ON  THE  ETIOLOGY  OF  MICROBIAL 
DISEASES 

I.   The  Ideas  on  Contagion  Prior  to  1866 225 

II.  Causes  of  the  Sterility  of  the  Ideas  Upon  Contagion  .    .   230 

III.  Anthrax:  Pollender,  Brauell,  Delafond .   233 

IV.  Davaine 237 

V.  Koch:  The  Spore  of  Anthrax 241 

VI.   Objections  to  the  New  Doctrine 244 

VII.  Pasteur:  The    Bacteridium    is    the    Sole    Cause    of 

Anthrax 250 

VIII.   Conflict  of  the  Microbe  with  the  Organism 253 

IX.   The  Septic  Vibrio 257 

X.   A  Common  Microbe  may  be  Pathogenic 263 

XI .  New  Examples  of  Physiological  Conflicts 269 

EIGHTH  PART 

THE  STUDY  OF  VIRUSES  AND  VACCINES 

I .  Microbial  Diseases  and  Virus  Diseases 273 

II.  Chicken  Cholera 276 

III .  Discovery  of  Vaccines 280 

IV.  Anthrax  is  also  a  Virus  Disease 285 

V .  Studies  on  Rabies  .    .  ■ 294 

VI.   The  Problem  of  Immunity 299 

VII.  Virulence  and  Attenuation 304 

VIII .  Return  to  Virulence 308 

IX.  Chemical  and  Humoral  Theories  of  Immunity 312 

X.  Cellular  Theory  of  Immunity -  317 

Annotated  List  of  Persons  Mentioned  in  this  Book  .   .   .  323 
Index 353 


EMILE   DUCLAUX 

(About  1897) 

(From  a  photograph  by  Paul  Rives,  Paris.) 


INTRODUCTION 

This  book  is  more  than  a  critique  of  Pasteur.  Itvis  a 
contribution  to  the  biological  history  of  a  swiftly  changing 
time,  a  very  striking  period  in  the  development  of  science. 
As  such  it  should  be  of  interest  to  all  biologists,  and 
especially  to  all  teachers  and  students  of  biology  and  of 
medicine.  For  them  it  was  written,  and  translated.  In 
this  time  of  world  upheaval  and  readjustment,  when  our 
young  men  are  looking  more  and  more  to  France  for 
moral  and  intellectual  ideals,  it  seems  peculiarly  apropos 
that  the  scientific  life  of  one  of  her  greatest  sons,  to  whom 
the  whole  world  owes  an  enormous  debt  of  gratitude, 
should  be  set  before  them  clearly  and  interestingly. 

This  life  of  Pasteur  was  published  in  1896,  and 
its  author  has  been  dead  fifteen  years.  The  book  speaks 
for  itself,  but  in  giving  to  the  public  an  English  edition 
it  seems  fitting  to  say  some  words  respecting  its  author  : 
"Cette  grande  et  belle  intelligence,  si  simple  et  si  robuste'1 
(  Youriévitch) . 

The  senior  translator  still  remembers  with  what  un- 
expected and  keen  pleasure  a  dozen  years  ago  he  saw  the 
title  of  this  book  in  a  German  catalogue  of  second-hand 
books.  For  some  unexplained  reason  he  had  never  come 
across  the  book  in  aDy  library  or  seen  any  notice  of  it  in 
any  review,  nor  could  he  find  any  of  his  fellows  who  had 
read  it,  or  seen  it,  or  even  heard  of  it.  Once,  only,  since 
then  has  he  seen  it  mentioned  in  a  catalogue  of  second- 
hand books.  Indeed,  it  seems  almost  as  if  it  must  have 
died  still-born,  so  little  notice  has  been  taken  of  it,  at 
least  outside  of  France.  Duclaux's  name  was  enough, 
however,  and  it  was  ordered  straightway,  with  the  fear, 
oft  renewed  during  the  next  few  weeks,  that  like  many  a 


VI  INTRODUCTION 

coveted  treasure  mentioned  in  old-book  catalogues,  it 
would  be  snapped  up  by  another  and  never  delight  his  eyes. 
But  such  was  not  to  be  the  case.  In  due  time  it  came 
(pages  uncut)  and  then  what  keen  delight  was  his  as  he 
devoured  page  after  page,  marveling  more  and  more  at 
the  wonderful  breadth  and  perspicacity  of  the  presenta- 
tion. Pasteur  seemed  alive  in  its  pages,  and  Duclaux 
not  less  alive.  No  book  about  a  scientific  man  ever  in- 
terested him  more,  or  could  be  written,  it  seemed,  with  a 
more  appreciative  and  discriminating  touch.  When  the 
last  page  was  finished  nothing  was  more  natural,  there- 
fore, than  to  write  on  its  margin  :  "The  most  useful  book 
I  have  read  in  a  long  time." 

Going  over  these  pages  ten  years  later,  the  writer  sees 
no  reason  for  modifying  his  first  judgment.  The  next 
impulse  was  to  lend  the  book,  and  then  to  wish  that  it 
might  reach  thousands  of  readers  in  a  suitable  English 
dress.  This  idea  disturbed  his  spirit  so  much  that  finally 
he  began  a  translation,  dictating  to  a  stenographer  in  the 
odd  minutes  of  a  busy  life.  Later,  it  seemed  better  to 
turn  over  a  part  of  this  work  to  an  assistant.  Eventu- 
ally, about  two-thirds  of  the  rough  draft  from  the  French 
was  made  by  Florence  Hedges.  We  then  worked  it  over 
together  into  its  present  English  shape,  but  those  who 
can  read  it  in  the  French  are  advised  to  do  so,  since,  do 
the  best  we  could,  Duclaux's  wonderful  idiomatic  style 
has  lost  somewhat  in  the  translation. 

If  Pasteur  be  an  incomparable  genius,  Duclaux,  at 
least,  is  his  Boswell,  but  he  is  more  than  a  mere  Boswell 
tagging  around  after  a  great  man.  He  is  himself  a  great 
man.  He  has  a  genius  of  his  own  which  burns  with  a  very 
clear  flame — a  genius  that  penetrates  and  illuminates 
whatever  it  touches,  and  this  has  made  him  an  incompar- 
able biographer,  and  one  of  an  unusual  kind.  He  is  no 
blind  partisan  or  patriot.     He  thinks  his  own  thoughts, 


INTRODUCTION  Vil 

goes  the  shortest  way  to  the  heart  of  a  subject,  and  im- 
presses one  everywhere  as  honest  and  fair  in  his  scientific 
criticisms.  He  is  an  ideal  man  of  science  and,  moreover, 
he  has  what  many  lack,  a  direct,  forcible,  and  delightful 
way  of  putting  things.  One  would  like  to  know  more 
about  such  a  man,  and  Madame  Duclaux  in  her  inter- 
esting book  ("I  like  it  best  of  all  the  books  I  have 
written,"  she  said)  has  opened  the  way.  In  the  spirit 
of  her  happy  motto  Transire  benefaciendo,  and  mostly 
from  this  heart  book,1  I  have  compiled  the  following 
facts  respecting  the  author  of  "Pasteur:  Histoire  d'un 
Esprit." 

Duclaux  was  Auvergnaise.  He  was  born  in  1840  in 
Aurillac  in  Cantal.  Aurillac  is  a  quaint,  gray-stuccoed, 
red-roofed  town  on  a  high  plateau  in  the  old  volcanic 
region  of  southern  France.  It  is  in  a  smiling,  pastoral 
country,  overlooked  by  the  great  rounded  flanks  of  the 
extinct  volcanoes.  It  is  in  latitude  45°,  due  south  of 
Paris  442  kilometers,  and  north  of  the  eastern  Pyrenees 
275  kilometers.  East  and  west  it  lies  about  midway  be- 
tween Bordeaux  and  the  Rhone  at  Valence.  Already 
the  population  begins  to  be  southern  in  its  speech  and  its 
manners. 

On  both  sides  Duclaux  was  descended  from  the  great 
middle  class  of  France.  His  father  was  a  clerk  with 
wandering  and  scholarly  proclivities,  a  dreamy  and  silent 
man.  His  mother  was  a  good-natured,  joyous,  affec- 
tionate country  girl,  the  daughter  of  a  small  proprietor 
and  merchant.  He  was  the  first  child.  From  his  ear- 
liest days  he  was  brought  up  very  strictly.  His  father, 
Pierre-Justin  Duclaux,  gave  nearly  his  whole  time  to  his 
education,  himself  teaching  him  at  first,  and  later,  when 
he  was  under  other  instructors,  going  over  all  his  lessons 

1  La  vie  de  Emile  Duclaux,  Par  Madame  Emile  Duclaux  (Mary  Robin- 
son).    Laval.  L.  Barnéoud  and  Cie  Imprimeurs.    1906.    12  mo.,  pp.  332. 


Vlll  INTRODUCTION 

with  him.  Emile  was  the  apple  of  his  eye;  on  him  was 
lavished  all  his  interest,  rather  to  the  neglect  of  the  other 
children  who  were  allowed  to  play  as  they  would  while 
Emile  must  stick  to  his  lessons,  to  become  the  scholar  of 
the  family.  In  this  respect  the  father  was  a  second 
James  Mill  or  Etienne  Pascal.  "  Sometimes,  Mamma, 
taking  pity,  sent  to  inquire  after  the  young  recluse.  The 
little  brothers  entered  the  study  softly  and  waited  re- 
ligiously ,  until  they  were  spoken  to.  Sometimes  they 
found  the  scrivener  drawing  up  a  legal  paper,  but  more 
often  they  saw  him  seated  at  the  work-table  of  his  son 
explaining  to  him  some  old  author.  The  opportune 
moment  come,  the  children  clasped  the  knees  of  the 
father  and,  while  he  stroked  their  heads  with  a  distracted 
hand,  he  said:  'You  have  come  for  Emile?  but  he  can- 
not go  yet.  Especially  do  not  talk!'  And  the  lesson 
went  on  and  on,  until  the  two  lads,  desperate,  withdrew 
on  tiptoe,  leaving  the  elder  to  his  endless  task."  *  *  *  * 
"Father  dreamy,  incommunicative;  mother  sensitive 
and  lively.  Such  without  doubt  is  an  excellent  com- 
bination for  the  production  of  a  superior  man.  Such 
at  least  were  the  parents  of  Louis  Pasteur  and  such  those 
of  Ernest  Renan." 

From  his  father  he  inherited  a  character  of  rare  eleva- 
tion, an  absolute  sincerity,  and  a  spirit  at  once  per- 
spicacious and  free,fa  little  inclined  to  criticise,  which 
made  him  so  "generous"  in  the  sense  of  Descartes;  but 
it  was  from  his  mother,  the  amiable  Agnes  Farges,  that 
he  inherited  that  overflowing  goodness,  the  openness  of 
mind  which  he  blended  with  so  fine  a  sagacity,  the  ban- 
tering good  nature,  always  tender  so  that  it  did  not 
wound.  What  he  had  of  skillful  and  prudent  in  his 
character  came  also  from  his  mother. 

The  child  loved  his  two  parents  equally,  confided  all 
his  thoughts  to  his  father  and  drew  the  sweetness  of  life 


INTRODUCTION  IX 

from  contact  with  his  mother.  In  return  for  a  devotion 
without  bounds,  the  father  exacted  implicit  obedience 
and  the  son  never  disobeyed  him.  If  he  felt  at  times  the 
constraint,  which  made  of  him  an  infant  prodigy  at  the 
expense  of  his  liberty,  he  never  mentioned  it,  but  spoke 
often  of  his  father  and  always  with  tenderness  and 
veneration. 

He  entered  college  at  Aurillac,  where,  in  1852,  he 
carried  off  the  first  prize  for  Spanish,  as  one  might  ex- 
pect from  a  son  whose  father  had  wandered  much  in 
Spain.  Every  evening  he  read  some  pages  of  Don 
Quixote  with  his  father,  who  was  the  authorized  trans- 
lator for  the  law  courts.  Through  all  his  college  studies 
the  father  kept  pace  with  him,  rising  at  4  or  5  o'clock  in 
the  morning  to  study  over  Emile's  college  lessons.  Again 
in  the  evenings,  the  supper  finished,  the  father  and  son 
climbed  up  to  the  study,  lighted  the  3-wick  lamp,  the. 
antique  liin,  and  began  the  evening's  lessons.  Once 
the  lessons  were  well  learned,  they  read  some  good  author 
from  the  treasure  of  old  books  the  scrivener  kept  in  his 
little  library.  There  were  some  volumes  of  the  Magasin 
Pittoresque  from  which  Emile  drew  his  first  notions  of 
science,  the  Letters  of  Madame  de  Sévigné,  the  Memoirs 
of  Saint-Simon,  the  plays  of  Racine,  a  volume  of  travels 
in  Spain,  a  little  history  in  two  volumes  of  the  Romans 
in  Gaul,  and  the  like. 

While  he  made  excellent  progress  in  his  classical  studies, 
he  was  fortunate  in  falling  under  the  influence  of  a  good 
teacher  of  mathematics  and  the  sciences.  Especially 
in  Balard's  pupil,  Emile  Appert,  who  was  at  the  same 
time  chemist,  physicist  and  geologist,  and  who  knew 
everything  and  how  to  teach  everything  and  turned  the 
boy's  mind  readily  from  the  classics  to  science,  he  found 
just  the  friend  he  needed. 

Studies  over,  father  and  son,  inseparable  still,  rambled 


X  INTRODUCTION 

over  woods  and  fields,  mountains  and  valleys.  To- 
gether they  discussed  rural  things  and  the  old  volcanic 
lands.  Emile  collected  pebbles  and  explained  to  his 
father  limestone  and  basalt,  and  together  they  read 
M.  Appert's  summaries.  The  neighbors  saw  them  pass  : 
the  father  tall,  erect  and  stern,  with  energetic,  wrinkled 
features,  the  son  meager  and  little,  always  holding  on  to 
his  father's  arm,  hitching  up  to  be  on  a  level,  talking  as 
they  went  along.  "What  can  they  find  to  talk  about  so 
much?  It  must  be  they  are  going  to  fish  for  crabs  in 
the  valley  of  the  Condamine?" 

Such  was  the  boyhood  of  this  man.  Between  his 
father  and  his  dear  M.  Appert  he  early  learned  to  love 
nature  and  especially  to  look  below  the  surface  of  things. 

The  supreme  desire  of  the  father  was  to  see  his  son 
enter  a  polytechnic  school  and  become  an  engineer  or  an 
officer  of  artillery.  To  enter  a  polytechnic  more  prepa- 
ration was  required  than  could  be  obtained  at  Aurillac. 
Clermont-Ferrand  and  Toulouse  were  considered  but  it 
was  finally  decided  that  he  should  go  to  Paris,  although 
it  wrung  the  father's  heart  to  be  parted  from  him.  Here 
he  studied  under  a  certain  M.  Barbet,  who  predicted  for 
him  a  brilliant  future  and  was  always  holding  up  to  him 
as  a  model  a  certain  Louis  Pasteur,  a  graduate  twenty 
years  earlier  from  the  same  institution  and  the  pride  of  the 
school,  who  had  just  left  the  faculty  of  Lille  to  take  charge 
of  the  scientific  studies  of  the  Normal  School  in  Paris. 

For  his  pocket  money  at  this  time  Duclaux  had  50 
francs  a  trimester.  Out  of  this  meager  sum  in  the  spring 
of  1858  he  took  35  francs  for  lessons  in  diction  and  for 
drawing  instruments,  and  for  his  nostalgia  ordered  an 
English  book,  Scrope's  Extinct  Volcanoes  of  Central 
France,  which  to  his  astonishment  cost  him  another 
30  francs  and  required  dire  economies  but,  in  the  delight 
of  possession,  was  worth  much  more  than  it  cost. 


INTRODUCTION  XI 

In  1859  Duclaux  successfully  passed  entrance  examina- 
tions for  both  the  Polytechnic  School  and  the  Normal 
School,  and  M.  Barbet  had  sufficient  influence  to  cause 
him  to  be  sent  to  the  latter. 

At  the  age  of  19,  therefore,  Duclaux  entered  the  Nor- 
mal School  and  came  under  the  teachings  of  Louis 
Pasteur.  The  father,  meanwhile,  had  died.  Each  anni- 
versary of  the  father's  death  the  young  man  went  to 
pass  with  his  mother  in  Aurillac.  But  another  bond  had 
sprung  up — an  enthusiastic  respect  for  the  man  of  genius 
who  was  now  sub-director  of  scientific  studies  in  the 
Normal  School.  After  Duclaux,  father  and  son,  it  was 
Pasteur  and  Duclaux.  From  the  beginning  Duclaux 
ranged  himself  under  his  banner  and  experienced  to  the 
depths  an  influence  which  modified  his  whole  mind  and 
thought,  as  it  was  later  to  overturn  all  science.  The 
chemists  of  the  Normal  School  of  1860  believed  in  Pasteur 
as  the  romanticists  of  1830  believed  in  Victor  Hugo,  and 
these  are  the  two  great  Gallic  names  of  the  19th  century. 
When  Duclaux  received  his  degree  from  the  Normal 
School  in  1862  he  entered  the  laboratory  as  assistant 
to  the  master,  assistant  in  a  double  sense,  since  the 
authorities  had  not  appointed  any  other  assistant  to 
sweep  up  the  dust  or  to  wash  the  glassware.  But  as 
Duclaux  said  later  in  his  charming  article  on  the  labora- 
tory of  Pasteur  which  he  contributed  to  the  book  on  Le 
Centenaire  de  V École  normale,  "It  is,  moreover,  a  useful 
apprenticeship  for  a  young  scientific  man  to  keep  things 
clean.  I  will  add,  although  it  is  perhaps  a  vanity  to  be 
condemned,  that  I  believe  I  have  never  had  flasks  as 
meticulously  cleaned  as  in  that  far  off  time  when  I 
cleaned  them  myself." 

Madame  Duclaux  has  drawn  a  very  pleasing  picture 
of  him  as  he  was  at  this  time: 

"I  possess  a  photograph  taken  at  this  period  which 


Xll  INTRODUCTION 

shows  him  very  young,  slender  and  alert,  with  the  supple 
figure  of  a  mountaineer.     He  is  rather  small,  he  has  very 
delicate  members,  especially  his  hands,  which  seem  to 
think.     His  manner  of  walking  is  full  of  a  self-restrained 
alacrity.     His  head  is  large  with  a  good  cranial  capacity, 
finely  formed,  bristling  with  dark  brown  hair  cut  close 
and  planted  low  and  tufted  around  a  perpendicular  fore- 
head which  is  ample  but  not  high.     The  mask  is  a  little 
melancholy,  elongated  as  in  portraits  of  the  sixteenth 
century.     In  this  thin  visage  there  are  fine  eyes,  very 
blue,  by  turns  dreamy,  teasing,  tender  or  profound  but 
always  limpid.     If  the  eyes  suggest  poetry,  the  long  nose 
stands  for  sagacity  and  goodness,  although  the  fleshy 
end  trembles  in   moments   of  impatience.     Fine  ears, 
elongated  at  the  tip  like  those  of  a  faun,  give  to  this  grave 
oval  head  of  the  thinker  a  delicately  rustic  character. 
Already  he  had  the  air  which  I  loved  so  much,  a  modest, 
ardent  and  good  expression.     Something  of  the  harsh 
accent  of  Cantal  still  vibrated  in  his  voice  in  spite  of  the 
lessons  in  diction  taken  at  the  Institution  Barbet  and  at 
the  Normal  School.     'Say  terrrine,  Duclaux,'  Madame 
Pasteur  will  often  say  to  him,  laughingly.     The  young 
man  spoke  well  and  sometimes  copiously,  with  charm 
and  spirit,  but  of  his  personal  ideas  he  was  not  very  com- 
municative, being  timid  as  well  as  independent.     He 
gave,  however,  an  impression  of  joyousness  when  one 
looked  at  him,  going  and  coming  from  one  piece  of 
apparatus  to  another,  humming  some  arietta  of  Mozart 
or  the  refrain  of  a  popular  song  heard  in  the  street." 

At  this  time  Pasteur  worked  in  very  cramped  quarters 
in  the  rue  d'Ulm.  From  such  quarters,  hardly  fit  for  a 
rabbit  hutch,  as  Duclaux  said,  started  the  movement 
which  was  to  revolutionize  science.  Here  in  the  Nor- 
mal School  Duclaux  was  lodged,  fed  and  received  as 
compensation  47  f  r.-50  per  month.     But  what  are  wages 


INTRODUCTION  Xlll 

when  one  can  be  with  a  master!  Raulin  was  his  prede- 
cessor, a  ferocious  anti-clerical.  Mascart  and  Gernez 
were  also  assistants  in  the  Normal  School  at  this  time 
and  friends  of  Duclaux,  especially  the  latter. 

These  were  the  heroic  times  of  the  Pasteurian  struggle. 
The  master  was  in  the  forefront  of  the  debate  on  crystals, 
the  campaign  on  fermentations  and  the  great  battle  over 
spontaneous  generations. 

In  October,  1865,  Duclaux  left  Paris  for  Tours,  where 
he  had  been  appointed  professor  of  chemistry  in  the  sec- 
ondary school.  He  now  had  the  maintenance  of  the 
family  on  his  hands.  He  was  the  youngest  professor  in 
the  faculty  of  France,  being  only  26.  From  Tours  he 
was  soon  transferred  to  a  better  place  at  Clermont- 
Ferrand,  where  a  portion  of  his  time  could  be  given  to 
Pasteur's  work.  When  Duclaux  was  seeking  this  trans- 
fer Gernez  interested  himself  in  behalf  of  his  friend  and 
was  very  much  surprised  and  chagrined  one  day  to  learn 
that  he  had  himself  been  appointed  to  the  place.  This 
appointment  he  would  not  accept  nor  would  Duclaux, 
under  the  circumstances,  until  Pasteur  smoothed  things 
out  by  taking  Gernez  with  him  to  Alais,  which  left 
Duclaux  free  to  accept  the  position  at  Clermont-Ferrand, 
a  fine  old  city,  former  capital  of  Auvergne  and  the  birth- 
place of  Blaise  Pascal. 

At  Clermont  he  had  about  a  hundred  students,  mostly 
medical  students.  The  pick  of  these  he  admitted  to 
his  own  laboratory  and  initiated  into  the  experimental 
method.  Sundays  he  went  with  these  choice  spirits  on 
long  excursions  through  the  volcanic  lands.  His  most 
distinguished  pupil  was  Emile  Roux,  the  present  director 
of  the  Pasteur  Institute,  who  says,  "  During  these  hours 
of  life  in  the  open  air  Duclaux  was  the  most  delightful 
of  companions,  overflowing  with  a  deep  spontaneous 
gaiety.     The  day  ended  around  the  hospitable  table  of 


XIV  INTRODUCTION 

Mamma  Duclaux  in  the  apartment  in  the  rue  Montlosier. 
It  was  truly  good  fortune  for  a  beginner  in  science  to 
meet  a  master  like  Duclaux.  "  In  connection  with  Roux, 
as  beginner  in  chemistry,  we  have  the  following  story. 
Duclaux  had  given  out  a  pinch  of  some  salt  for  analysis. 
"  What  is  it,  my  friend?"  and  the  test  made,  the  young 
man  replied,  "Sir,  I  think  it  is  sulfate  of  copper."  "  Ah, 
you  think  so?  Truly?  Eh,  well,  do  it  over  again." 
At  the  end  of  some  hours,  the  pupil  returns,  "Sir,  I 
believe  it  is  sulfate  of  copper."  " Begin  again,  my 
friend."  But  the  third  time  he  returns  with  indignation 
in  his  eyes  and  voice  a  little  vibrant  as  he  says:  "Sir, 
it  is  sulfate  of  copper."  "So  it  is,  my  friend,  but  you 
see  in  chemistry  it  is  necessary  to  know,  not  merely  to 
believe  or  to  think." 

From  Clermont-Ferrand,  Duclaux  went  to  Lyons, 
where  he  remained  five  years  as  professor  of  physics,  and 
then  to  Paris  (1878)  as  professor  of  meteorology  in  the 
Agronomic  Institute.  Through  all  of  these  changes  it 
was  bio-chemistry  which  held  the  first  place  in  his  affec- 
tions, but  he  was  geologist,  physicist,  meteorologist, 
agronomist,  and  chemist,  as  well  as  learned  in  medicine, 
in  brewing  and  in  the  dairy  industries.  He  loved  to 
contemplate  one  aspect  of  the  universe  as  well  as  another. 
To  his  friend  M.  Voigt  he  writes  at  this  time  from  one 
of  his  summer  vacations  in  Fau.  "I  like  the  solitude 
where  I  live  so  well  that  I  imagine  it  ought  to  have  as 
much  charm  for  my  friends.  I  find  myself  particularly 
happy  in  the  country.  Free  labor  and  not  at  all  pressing, 
an  independent  life,  very  few  books,  almost  no  journals, 
see  how  I  regain  possession  of  myself." 

At  another  time  he  wrote:  "I  am  strongly  attached 
to  the  soil.  I  communicate  with  it.  I  think  how  many 
generations  of  my  fathers  have  lived  in  contact  with  it 
and  I  take  pleasure  in  asking  it  about  them.     I  never 


INTRODUCTION  XV 

come  across  a  wall  of  big  dry  stones,  a  retaining  wall 
made  to  gain  a  few  inches  of  earth,  an  irrigation  ditch, 
an  old  tree  sensing  decrepitude,  a  big  rock  in  a  field, 
without  thinking  of  all  those  who  have  builded  and 
planted  and  dug,  or  grumbled  at  having  to  pass  around 
the  rock  they  could  not  remove.  With  such  ideas  and 
impressions,  there  is  no  solitude.  I  live  in  communion 
with  my  own,  and  with  this  soil,  on  which  they  have 
left  the  powerful  impression  of  their  feeble  intelligences 
and  their  vigorous  arms." 

At  Paris  he  displayed  incredible  activity — mornings 
and  evenings  at  his  work-table  and  the  rest  of  the  day 
either  at  the  Agronomic  Institute  or  at  the  Sorbonne 
(Roux).  These  were  sad  years  and  labor  was  an  opiate. 
He  overworked  and  suffered  from  insomnia  and  for  two 
years  from  boils.  During  this  time  he  wrote  "Ferments 
et  Maladies''  (1882)  which  he  dedicated  to  his  wife  who 
had  died  of  puerperal  fever.  "  To  you,  innocent  victim 
of  the  infinitely  little,  I  dedicate  this  book  in  which  I 
have  attempted  to  popularize  their  history.  May  it, 
slight  as  it  is,  serve  to  hasten  a  little  the  day  wherein 
the  accomplishment  of  her  sacred  mission  will  no  longer 
cause  the  wife  to  fail  her  husband,  and  the  mother  the 
new-born  child."  The  book  made  a  sensation  and  a 
gold  medal  was  struck  for  it  by  the  Society  of  Agricul- 
ture; also  a  number  of  medical  men  were  won  over  to  a 
belief  in  microbes. 

Duclaux  loved  to  ripen  a  project  for  a  long  time  in  his 
mind  and  to  work  it  over  and  over  on  paper  before 
finally  putting  it  into  type,  which  is  the  secret  of  all 
good  expression.  This  was  Tennyson's  method  and 
Renan's.  It  was  Beethoven's  way  in  music.  It  is  also 
the  method  of  Anatole  France. 

In  1882,  apropos  of  "Ferments  et  maladies"  which  had 
just  appeared,  he  wrote  to  his  friend,  M.  Voigt,  "You 


XVI  INTRODUCTION 

are  very  amiable  to  say  so  many  good  things  about  my 
book  *  *  *  but  physicians  are  those  I  would  wish  to 
lay  hold  of  and  I  begin  to  believe  that  I  shall  not  suc- 
ceed !  I  know  very  well  that  old  physicians  do  not  read 
any  more,  and  when  they  do  read  do  not  understand.  I 
know  that  students  think  only  of  their  examinations, 
when  they  think  at  all;  but  among  the  population  of 
hospital  internes  or  externes  and  that  of  physicians  who 
have  not  yet  obtained  a  clientele,  I  thought  I  should 
find  attentive  readers  possessed  of  good  will.  Experience 
begins  to  demonstrate  that  I  shall  not  have  them." 
Again  he  writes:  "When  I  read  one  of  those  byzantine 
discussions  of  the  Academy  of  Medicine  always  I  ask 
myself  whether  the  speakers  do  not  wish  to  understand 
or  simply  cannot  understand."  In  1885  his  book  "Le 
Microbe  et  la  Maladie"  was  completed  and  was  published 
the  following  year.  This  year  he  writes,  '  '  My  dear  friend, 
Medicine  is  a  strange  terrain.  It  is  an  edifice  where 
nothing  remains  standing.  Tradition  still  maintains 
the  plan  and  general  arrangement,  but  it  would  be  best 
that  everything  should  come  down,  because  there  is  no 
good  to  be  derived  from  what  exists  except  from  the 
materials.  If  I  were  a  physician  I  believe  I  should  give 
the  mattock  blow  which  would  make  all  crumble.  Since 
my  manuscript  is  finished  I  have  become  more  intimately 
aware  of  the  fragility  of  medical  notions  even  those  in 
appearance  best  founded.  Who  knows?  Perhaps  a 
section  of  wall  will  blow  up  somewhere  and  a  little  light 
penetrate  through  the  opening  thus  made." 

From  1877  to  1896  Duclaux's  time  was  largely  de- 
voted to  a  profound  study  of  milk  and  dairy  products. 
These  studies  led  him  to  attribute  a  preponderating  rôle 
to  microbes  in  all  the  industries  based  upon  milk.  His 
work  in  Cantal  led  to  a  revolution  in  cheesemaking  and 
to  a  great  extension  of  the  industry,  due  to  the  better 


INTRODUCTION  XV11 

keeping  qualities  of  the  properly  made  cheeses.  "The 
work  of  Duclaux  inaugurated  the  scientific  era  in  the 
dairy  industry"  (Dr.  Roux).  In  recognition  of  the  im- 
portance of  these  researches  the  Agricultural  Society 
awarded  him  its  great  gold  medal  in  1881. 

Duclaux  was  also  the  first  to  gather  together  and 
coordinate  the  scattered  facts  on  the  enzymes.  This  he 
did  in  1877  for  Dr.  Dechambre's  "Dictionnaire  des 
sciences  médicales."  Some  pages  sufficed  at  this  time, 
but  in  1899  when  he  took  up  the  subject  again  for  the 
second  volume  of  his  "  Traité,"  seven  hundred  and  fifty 
pages  were  insufficient.  "He  returned  to  this  subject 
many  times,  showing  how  the  same  microscopic  organism 
secretes  different  enzymes,  according  to  the  food  that  is 
given  it.  He  classed  the  enzymes  by  the  reactions 
they  cause  and  proposed  the  terminology  adopted 
to-day"  (Dr.  Roux). 

He  also  devoted  much  time  to  the  purity  of  water 
supplies  and  to  analyzing,  especially  during  vacations  in 
the  latter  part  of  his  life,  the  water  of  springs  issuing 
from  the  volcanic  lands,  and  said  that  he  could  tell 
whether  the  water  had  percolated  over  limestone  or 
basalt. 

Also  toward  the  close  of  his  life  he  became  greatly 
interested  in  community  welfare,  attended  conferences, 
presided  at  meetings,  made  addresses,  and  wrote  the 
charming  book  "L'hygiène  sociale." 

In  1888  when  the  Pasteur  Institute  was  founded  the 
workers  in  the  rue  d'Ulm  had  only  to  transport  their 
microscopes  and  their  balances  to  rue  Dutot,  but  there 
was  need  of  someone  not  to  make  discoveries,  all  could 
do  that,  but  to  disseminate  them  and  to  formulate  a  body 
of  doctrines.  Duclaux  was  selected  for  this  purpose  The 
other  colleagues  of  this  time  were  Chamberland,  Roux, 
Nocard;  Perdrix,  assistant  professor;  Loir  and  Fernbach, 


XV111  INTRODUCTION 

assistants;  Grancher,  Chantemesse,  and  Charrin,  physi- 
cians in  charge  of  the  antirabic  inoculations  ;  and  Eugene 
Viala,  devoted  assistant  in  the  rabies  service.  Also  a 
little  later  Metchnikoff  and  Yersen  formed  part  of  the 
staff,  but  Strauss  had  gone  earlier  to  a  chair  in  the  Med- 
ical School.  Pasteur  was  now  66,  and  the  sole  shadow 
on  the  picture  was  the  ill  health  of  the  master.  If 
Pasteur  had  not  been  weakened  by  his  second  attack  of 
paralysis  in  1887,  the  new  Institute  might  have  been 
very  different  from  what  it  is  to-day,  namely,  a  great 
cooperative  research  institution  drawing  the  brightest 
minds  from  all  parts  of  France  and  all  quarters  of  the 
globe.  It  might  have  been  greater,  at  first,  but  on  the 
death  of  the  master  all  would  have  crumbled.  Its  pres- 
ent form,  so  cohesive  while  at  the  same  time  so  well 
adapted  to  maintain  the  independence  of  the  workers, 
corresponds  rather  to  the  ideas  of  the  collaborators  than 
to  those  of  Pasteur  and  is  due  largely  to  the  administra- 
tive genius  of  Duclaux  on  whom  fell  nearly  the  whole 
burden  of  the  organization.  Duclaux  wished  to  make  it 
an  immense  college  of  international  biology,  whereas 
Pasteur's  idea  was  rather  to  make  it  a  place  where  he 
would  work  behind  closed  doors  with  rare  and  devoted 
assistants,  not  explaining  too  fully  the  reason  for  his 
demands  but  being,  like  an  Indian  god,  one  head  with 
many  hands.     Our  good  English  poet  has  said: 

"The  old  order  change th,  yielding  place  to  new 

And  God  fulfils  himself  in  many  ways, 

Lest  one  good  custom  should  corrupt  the  world." 

So  it  was  to  be  here.  The  old  master,  the  founder,  was 
not  always  in  perfect  accord  with  his  friend.  Duclaux 
wished  to  open  all  the  doors,  call  the  faithful  from  all 
corners  of  the  earth,  work  in  a  large  way,  found  a  scien- 
tific college  for  the  future,  where  each  one  would  be  free 


INTRODUCTION  XIX 

while  laboring  in  a  common  cause.  The  professor  and 
the  social  apostle  dominated  in  him.  Pasteur  was 
especially  a  discoverer.  Original,  profound  and  slow, 
he  was  made  to  walk  alone.  He  said  "we  must  seek." 
His  disciple  added  "we  must  organize  and  convince." 
Roux  understood  both  points  of  view,  went  from  one  to 
the  other,  and  effected  a  reconciliation,  for  each  one 
maintained  his  own  ideas  only  in  the  interest  of  the 
foundation.  And  so  the  years  passed  on,  each  year 
giving  more  and  more  into  Duclaux's  shaping  hand,  until 
the  Institute  became  such  as  we  see  it  to-day. 

"To  this  great  foundation  Pasteur  bequeathed  a  sci- 
entific tradition  but  it  was  Duclaux  who  created  its  soul" 
(Bloch).1 

One  of  Duclaux's  first  efforts,  begun  even  before  the 
Institute  was  opened,  was  the  founding  of  a  journal 
which  should  be  a  worthy  exponent  of  the  new  ideas. 
Thus  came  into  being  in  1887  "Les  Annales  de  VInstitut 
Pasteur"  which  has  done  so  much  for  the  advancement 
of  human  and  comparative  pathology,  and  to  which 
Duclaux  devoted  all  of  his  energy  and  ability.  In  this 
journal,  the  first  volume  of  which  was  organized  around 
the  doctrine  of  immunity,  he  realized  an  old  dream  of 
Raulin,  his  comrade  of  other  days. 

In  many  ways  Duclaux's  interests  deepened  and  diver- 
sified in  these  years.  In  1888  he  became  a  member  of 
the  Academy  of  Sciences,  in  the  section  of  rural  economy. 
In  1890  he  entered  the  National  Society  of  Agriculture. 
In  1894  he  was  elected  a  free  member  of  the  Academy  of 
Medicine.     And  always  there  were  his  Annales. 

"  My  journal  (1892)  gives  me  twice  as  much  work  since  it  threatens 
to  become  twice  as  large  as  at  the  beginning.  I  have  two  laboratories 
to  conduct  with  two  categories  of  students.  In  short  I  am  driven: 
"0  rus  quando  te  aspiciaml" 

annuaire  de  l'Association  des  anciens  élèves  de  l'École  Normale. 


XX  INTRODUCTION 

Pasteur  died  September  28,  1895,  and  the  Council  of 
the  Institute  elected  Duclaux  to  be  his  successor.  Noth- 
ing less  resembled  the  dreamy,  intuitive  nature  of  Pas- 
teur, turn  by  turn  combative  and  silent,  than  the  modest, 
passionate,  devoted  soul  of  his  apostle.  They  were  equal 
only  in  a  generous  ardor  of  soul  and  in  the  patient  tenac- 
ity which  both  gave  to  the  service  of  science.  Never- 
theless, it  was  Duclaux  of  all  the  Pasteurians,  who 
possessed  most  fully  the  entire  tradition  of  the  master, 
since  he  had  been  more  or  less  closely  associated  with  him 
and  familiar  with  his  ideas  since  1858. 

Nothing  was  more  natural  therefore  than  that  he 
should  write  a  book  on  Pasteur.  Even  before  the  Insti- 
tute was  thought  of,  Duclaux  wished  to  erect  in  his  own 
way  another  monument  to  the  memory  of  his  master. 
For  he  realized  how  fragile  is  life  and  that  already  many 
things  had  ceased  to  exist  except  in  his  memory.  There- 
fore, he  wrote  this  book:  u Pasteur:  Histoire  oVun  Esprit." 
In  it  the  Pasteurian  discoveries  unfold  in  their  harmo- 
nious development  with,  perhaps,  a  little  more  amplitude 
and  coherence,  a  little  less  originality  and  vivid  pro- 
fundity than  in  the  reality.  He  who  has  read  this  book 
will  understand  the  reach  of  the  greatest  scientific  move- 
ment in  the  nineteenth  century,  and  at  the  same  time  will 
appreciate  how  slowly  the  truth  unfolds  and  how  often 
genius  itself  loses  the  thread  of  the  labyrinth  in  traversing 
it  for  the  first  time.  Now  that  we  have  made  of  this 
daedalus  one  of  the  boulevards  of  the  modern  mind,  it 
is  good  to  recall  what  obstacles  and  what  errors  then 
rendered  it  almost  impracticable.  The  one  who  knew 
best  the  founder  of  microbiology  has  written  of  the  book 
as  follows:  "After  having  read  this  analysis  of  his  work, 
we  understand  Pasteur  better,  and  find  him  greater  still" 
(Dr.  Roux).  We  understand  better  both  Pasteur  and 
Duclaux.     Pasteur  followed  his  idea  as  the  magi  their 


INTRODUCTION  XXI 

star.  "He  was  a  priest;  priest  of  the  idea,"  said  his 
successor.  In  him,  instinct  or  rather  bold  intuition, 
dominated  reason.  "  Therefore,"  says  Duclaux,  "he  saw 
with  a  new  vision  and  justly."  His  disdain  for  tradi- 
tional knowledge  and  philosophical  speculations  was 
scarcely  concealed.  Trusting  only  in  experiments,  he 
knew  how  to  outstrip  them  and  more  than  once  went  far 
beyond  them.  "That  which  puts  him  outside  of  com- 
parison is  the  fact  that  he  loved  great  horizons,  knew 
how  to  discover  them  and  to  make  himself  a  part  of 
them;  that  he  saw  at  a  distance  and  through  the  mists, 
more  clearly  than  anyone  else,  the  high  summit  he  must 
attain  to  dominate  the  unknown  and  promised  land. 
This  was  his  rare  gift  and  the  secret  of  his  power.  But 
once  seen  he  had  wings  to  reach  it,  no  more  than  we. 
One  might  believe,  considering  the  originality,  the  sim- 
plicity and  the  unexpected  in  his  solutions,  that  they  were 
spontaneous  and  in  the  nature  of  happy  discoveries.  I 
do  not  know  whether  there  ever  are  any  such  easy  dis- 
coveries, accomplished  without  effort  and  by  a  sort  of 
divination.  Such  surely  was  not  the  case  with  Pasteur's. 
If  he  was  a  discoverer  it  was  first  of  all  because  he  was  a 
silent  man  and  an  obstinate  one."1 

Duclaux's  spirit  was  patient  and  methodical  but  much 
less  concentrated  than  Pasteur's.  He  discovered  rela- 
tively little,  but  he  excelled  in  understanding,  observing 
and  comparing.  Without  pride,  he  loved  obscure  labor 
— the  only  means  that  permits  a  great  soul,  unknown  of 
the  multitude,  to  enjoy  liberty  and  to  enter  into  the  de- 
lights of  meditation.  There  was  something  of  Mon- 
taigne in  the  vast  and  varied  intelligence  of  Duclaux. 
It  made  no  difference  to  him  whether  a  doctrine  or  a 
theory  was  true,  if  it  incited  to  labor  and  led  to  the 
discovery  of  new  facts.     He  made  use  of  criticism  and 

1  Duclaux.    Discours  aux  étudiants  de  Paris.     18  juin.  1896. 


XX11  INTRODUCTION 

hypothesis  to  interest  and  to  arouse,  as  an  electric  cur- 
rent to  stimulate  the  too  often  inert  substance  of  the 
human  brain.  He  said:  Je  voudrais  voir  tout  marcher 
autour  de  moi  du  même  train  que  moi.  In  his  "  Discours 
aux  étudiants"  he  has  expressed  himself  also  as  follows: 

"The  free  disinterested  search  for  truth  is  useful,  in 
and  of  itself,  from  the  delight  it  brings  to  the  one  who 
follows  it,  from  the  independence  of  spirit  it  begets,  from 
the  deep  sentiment  it  develops  of  liberty  and  of  respon- 
sibility. I  dare  maintain  even  for  this  inner  work  that 
it  has  no  need  of  looking  to  or  obtaining  the  suffrages  of 
other  men.  It  is  sufficient  that  we  have  the  conscious- 
ness of  being  in  our  place  and  of  doing  our  duty  honestly. 
'Live,'  said  Pasteur,  'in  the  serene  peace  of  the  labora- 
tories and  the  libraries.'  I  am  sure  of  remaining  faithful 
to  his  thought  in  adding  :  You  will  not  always  find  glory 
there,  you  will  never  find  fortune  there,  but  you  will 
experience  there  the  delight  of  every  day  being  something 
more  than  the  day  before,  and  of  having  brought  into 
the  world  your  share  of  the  truth." 

"Do  not  take  my  word  for  things  but  be  enamored  of 
independence,"  he  said.  "The  fruitful  periods  of  science 
are  those  in  which  dogmas  are  shaken." 

"You  esteem  me  too  highly,"  he  writes.  "  There  are 
a  hundred  thousand  Frenchmen  who  are  as  important  as 
I  am.  I  differ  from  them  only  in  that  I  have  been  helped 
more  by  science.  We  must  distinguish  between  those 
who  have  rare  qualities  and  those  who  march  in  the 
ranks  with  common  qualities,  made  productive  by  will 
and  labor." 

The  national  instruction,  he  said,  reflecting  on  the  war 
of  1870,  is  not  only  insufficient  but  false.  Based  on 
rhetoric  and  on  classical  studies,  it  ornaments  the  mind, 
but  does  not  strengthen  it  much;  rather  we  may  say  it 
weakens  it,  since  it  instills  the  principle  of  authority, 


INTRODUCTION  XxiU 

and  makes  all  rest  on  the  example  of  others,  whereas 
youth  should  be  accustomed  to  see,  to  scrutinize,  and  to 
feel  for  itself,  aided  to  draw  much  from  its  own  deeps, 
and  set  in  quest  not  of  elegance,  not  of  poetry,  but  of  truth. 
A  method  of  teaching  founded  on  science,  preaching  ex- 
amination and  research,  not  recoiling  from  the  minutiae 
of  analysis;  seeking  in  all  things  to  know  the  causes 
and  the  consequences,  leaving  nothing  to  chance,  culti- 
vating in  its  proteges  prudence  and  initiative,  such  a 
teaching  he  thought  would  give  to  France  a  new  existence. 

"I  have  tried  on  the  children  the  effect  of  abstract 
reasonings  (1886).  Alas,  they  do  not  comprehend  them, 
and,  if  other  children  resemble  them,  the  teaching  of  the 
exact  sciences  in  the  lower  grades  is  very  chimerical. 
They  want  the  concrete,  always  the  concrete." 

He  addressed  himself  to  their  understanding  and  their 
conscience  more  often  than  to  their  memory.  "In  an 
old  volume  of  Montaigne  at  Olmet  I  found  the  two 
fine  chapters  on  'l'Institution  des  Enfants'  full  of  penciled 
markings.  Such  an  education,  free,  strong  and  healthy, 
seemed  to  him  well  adapted  to  furnish  those  two  solid 
foundations  of  character — independence  and  sincerity. 
But  to  this  ideal  of  Montaigne  he  added  what  had  been 
the  ruling  principle  of  his  own  existence;  forgetfulness 
of  self  and  the  capacity  of  devoting  himself  to  a  high 
end.  To  be  a  free  man;  to  look  in  all  things  beyond 
selfish  interests;  to  love  the  truth  and  to  speak  it;  to 
act  comformably  to  what  seems  just;  to  be  mutually 
helpful.  These,  unless  I  am  deceived,  were  his  five 
commandments." 

His  ideas  on  many  subjects  are  full  of  interest:  "It 
is  precisely  because  science  is  never  sure  of  anything 
that  it  always  advances." 

"For  the  idea  of  specificity,  still  dominant  ten  years 
ago  when  I  wrote  the  first  edition  of  my  "  Traité  de  Micro- 


XXIV  INTRODUCTION 

hiologie"  has  been  substituted  another,  which  is  de- 
veloped in  my  present  book,  that  of  cellular  toleration." 

"Besides,  how  is  it  possible  not  to  see  that  the  immense 
edifice  on  which  we  all  labor  changes  constantly  in  plan 
and  in  foundations.  We  have  lovingly  hewn,  dressed 
and  even  sculptured  our  stone,  with  the  thought  that 
it  will  remain  perhaps  a  stone  of  the  façade,  and  attract 
the  attention  of  visitors.  Vain  hope,  new  tiers  of  ma- 
sonry will  cover  it  and  cause  it  to  be  forgotten.  It  mat- 
ters not!  It  exists,  and,  if  we  have  chosen  it  wisely 
and  built  it  solidly,  it  will  serve  as  the  foundation  of  new 
discoveries"  (Discours  aux  étudiants). 

Apropos  of  the  Dreyfus  affair,  in  which  he  sided  with 
Dreyfus,  took  public  action  and  suffered  correspondingly, 
he  writes: 

"We  also  have  rules,  which  have  descended  to  us  from 
Bacon  and  Descartes — not  to  lose  our  heads,  not  to  put 
ourselves  in  a  cave  in  order  to  see  better,  to  believe  that 
probabilities  do  not  count,  that  a  hundred  perhapses  are 
not  worth  a  single  certainty.  Then,  when  we  have  sought 
and  believe  that  we  have  found  the  decisive  proof,  even 
when  we  have  succeeded  in  making  it  accepted,  we 
are  resigned  in  advance  to  see  it  become  invalidated 
by  a  process  of  revision  over  which  often  we  ourselves 
preside." 

"In  all  this  we  are  very  far  from  the  Dreyfus  affair; 
and  truly  we  have  a  right  to  ask  if  the  State  does  not 
waste  its  money  on  educational  establishments,  the  pub- 
lic spirit  is  so  far  from  scientific."  *  *  * 

"If  Dreyfus  is  on  Devil's  Island,  it  is  only  because 
the  Government  has  listened  to  the  cries  of  the  mob  and 
joined  the  majority  instead  of  listening  to  the  minority, 
alone  capable  of  imposing  silence  on  the  human  brute." 

"It  has  a  tragic  grandeur.  Can  you  think  of  a  like 
drama,  played  by  a  nation,  with  that  freedom  of  the 


INTRODUCTION  XXV 

press  which  allows  the  whole  people  to  take  part  in  the 
drama?  It  is  two  tragic  choruses  berating  each  other. 
And  the  scene  is  France,  and  the  theater,  the  world." 

"The  minister  was  long  and  diffuse.  It  is  incredible 
how  much  this  cursed  French  language  allows  one  to 
speak  without  saying  anything.  There  are  a  certain 
number  of  words  which  straightway  show  the  intellectual 
poverty  of  those  who  use  them.  Ten  times  yesterday 
[at  the  unveiling  in  Lille  of  a  monument  to  Pasteur]  the 
rigid  logic  of  Pasteur  was  mentioned.  But,  good  people! 
logic  is  a  proof  of  mediocrity,  and  savants  who  have  only 
logic  are  not  scientific  men!' 

"Nature  loves  diversity,  education  aims  at  repressing 
it.  Those  who  later  break  through  into  life,  show  origi- 
nality and  make  a  name  for  themselves,  are  recruited 
chiefly  from  those  who  have  escaped  the  sterilizing 
influences  of  the  first  years." 

"Toute  douleur  est  bonne  si  elle  sert  à  nous  agrandir 
l'âme." 

"On  peut  rêver  une  humanité  supérieure  à  celle  qui 
s'incarne  temporairement  en  nous." 

"Soyons  chacun  soi-même,  soyons  différent  mais 
soyons  unis." 

"Ce  que  la  cellule  vivante  faisait,  sans  conviction  ni 
libre  arbitre,  il  était  digne  de  l'homme  de  le  faire,  dans 
l'intérêt  commun." 

"There  is  no  end  to  science.  So  long  as  there  shall 
be  men,  there  will  be  savants,  and  so  long  as  there  shall 
be  savants  there  will  be  discoveries.  Gradually  the 
spirit  of  men  of  science  has  been  enlarged  and  has  become 
open  to  the  idea  that  the  world  is  immense,  that  the 
forces  which  circulate  in  it  are  also  immense  in  number, 
that  those  of  which  we  are  ignorant  considerably  exceed 
those  we  know.  We  are  sure,  from  certain  examples, 
that  there  are  circulating  around  us  incessantly  count- 


XXVI  INTRODUCTION 

less  forces  of  which  we  are  ignorant1  and  will  remain 
ignorant  for  a  long  time,  things  with  which  other  beings 
than  ourselves  may  be  perfectly  familiar;  for  it  is  here 
that  we  find  that  imperfection  of  our  senses  which  does 
not  allow  us  to  draw  conclusions  from  ourselves  as  to 
other  beings  which  surround  us. 

"Do  not  defend  yourself  against  faith  and  confidence. 
Life  would  be  an  immense  dupery,  the  world  in  the  midst 
of  which  we  exist  would  be  a  colossal  absurdity,  if  the 
earth  were  the  only  abiding  place  and  if  what  is  best  in 
us  and  among  us,  should  be  lost  in  universal  nothingness. 
The  heavens  teach  not  only  the  glory  of  God,  they  teach 
also  hope  to  all  those  who  are  worthy  of  hope." 

Madame  Duclaux  closes  her  account  of  Duclaux  with 
these  words  in  which  many  of  us  will  concur:  "L'âme 
la  plus  modeste,  la  plus  désintéressée,  et  une  des  plus  justes 
de  ce  temps." 

The  following  translation,  which  I  have  made  from  the 
eulogy  on  Duclaux,  published  in  the  Annales  de  V Insti- 
tute Pasteur  for  May,  1904,  and  written,  it  is  said,  by 
Dr.  Roux,  his  former  student  and  his  successor  as  director 
of  the  Pasteur  Institute,  will  serve  as  a  fitting  close  to 
this  introduction: 

Once  more  the  Pasteur  Institute  is  in  mourning.  The 
third  of  this  month  died  Emile  Duclaux,  the  director  of 
this  Institute,  the  founder  of  these  Annales. 

"In  less  than  a  year,  Nocard  and  Duclaux  have  been 
taken  from  us! 

"All  those  who  have  frequented  the  Pasteur  Institute 

1  How  right  he  was  must  now  be  apparent  to  every  one.  Since  these 
thoughts  were  expressed  in  1901  has  come  most  of  our  knowledge  of  the 
radio-active  substances — uranium,  ionium,  radium,  actinium,  thorium 
and  their  emanations — and  all  of  those  revolutionary  ideas  on  the  nature 
of  electricity,  the  structure  of  matter  and  the  constitution  of  the  universe, 
which  now  fill  the  minds  of  scientific  men  with  awe  and  wonder. 


INTRODUCTION  XXV11 

will  understand  our  deep  sorrow,  for  they  know  the  sen- 
timents which  united  the  workers  of  this  institution  to 
its  director.  They  were  the  sentiments  of  confidence, 
respect  and  affection  which  a  true  chief  inspires. 

"After  Pasteur,  no  one  knew  better  than  Duclaux  how 
to  direct  this  Institute,  where  are  gathered  together 
young  scientific  men  whose  independence  he  knew  how 
to  respect  while  directing  their  efforts  toward  a  common 
end.  His  authority  was  beloved,  for  it  proceeded,  not 
from  his  position  but  from  the  qualities  of  his  mind  and 
his  heart.  One  went  to  him  when  he  felt  lost  in  the  ob- 
scurities of  a  scientific  research,  one  went  to  him  also 
when  he  felt  oppressed  by  the  miseries  of  life.  Confi- 
dence was  born  from  the  beginning,  so  cordial  was  his 
welcome,  so  much  the  luminous  glance  of  his  merry  blue 
eye  expressed  goodness.  Duclaux  soon  learned  what  you 
expected  of  him;  his  clear  intelligence  overcame  the  ob- 
stacle which  arrested  you  and  his  good  heart  always 
found  wherewith  to  comfort  you.  He  never  lost  an 
occasion  to  be  obliging.  On  leaving  him  one  always 
felt  stronger  for  scientific  struggles  as  well  as  for  moral 
struggles. 

"The  conversation  of  Duclaux,  simple,  full  of  imagery, 
full  of  original  ideas,  was  charming;  it  was  moreover 
beneficent,  because  it  allowed  a  character  of  rare  beauty 
to  show  through.  Thus,  this  man  so  jealous  of  his  inde- 
pendence, so  respectful  of  that  of  others,  became,  with- 
out suspecting  it,  a  director  of  consciences.  None  of  us, 
disciples  or  friends,  would  have  had  a  tranquil  spirit  if 
Duclaux  had  disapproved  any  of  his  actions. 

"Duclaux  owed  this  influence  to  the  fact  that  his  acts 
were  worth  even  more  than  his  words.  When  he  be- 
lieved a  thing  just,  nothing  would  have  prevented  him 
from  undertaking  it.  He  went  ahead  without  blowing 
a  trumpet,  without  considering  the  prejudices  that  would 


XXV111  INTRODUCTION 

be  overturned  any  more  than  the  blows  that  would  be 
received.  He  was  one  of  those  rare  men  who  support  a 
cause,  not  for  the  advantages  they  expect  to  receive,  but 
simply  because  they  believe  it  is  just.  Duclaux  sup- 
ported those  which  he  had  adopted  with  the  tenacity  of 
his  Auvergnaise  blood  and  also  with  a  force  of  thought 
and  clarity,  and  a  generous  joyousness  which  rendered 
his  faith  contagious.  As  to  attacks  against  himself,  he 
bore  them  with  an  imperturable  serenity;  this  scientific 
man  with  a  slender  body  and  frail  members  possessed 
true  courage,  and  he  possessed  it  to  the  degree  of  giving 
it  to  others  in  tragic  moments. 

" Goodness  and  the  disinterested  worship  of  justice  and 
of  truth  were  the  rules  of  his  private  life  as  they  were  of 
his  scientific  life.  It  was  a  delight  to  him  to  find  in  a 
memoir  new  facts  and  well-conducted  experiments.  If 
the  publication  was  that  of  a  young  man  his  joy  was  com- 
plete. He  showed  this  in  his  articles  in  the  Annales, 
which  were  marvels  of  exposition  and  of  criticism.  So 
much  so,  that  the  author  often  found  in  the  analyses  of 
Duclaux  more  than  he  had  himself  put  into  the  original. 

"In  order  to  make  the  labors  of  a  beginner  useful, 
Duclaux  did  not  hesitate  before  the  disagreeable  task 
of  retouching  the  manuscript,  pruning  it,  sometimes 
even  rewriting  it,  in  order  that  the  interesting  point 
might  stand  forth  clearly,  which  point  was  not  always 
that  one  which  the  author  had  believed. 

"His  penetrating  and  just  criticisms,  with  an  original 
and  piquant  turn,  never  wounded;  they  guided  into  the 
right  pathway  and  kept  from  vanity. 

"Correspondents  from  all  countries  sought  the  advice 
of  Duclaux  and  he  passed  a  good  part  of  his  time  in  inter- 
course with  them.  He  excelled  in  discovering  young 
talents  and  in  giving  to  them  a  knowledge  of  themselves. 
He  was  truly  a  midwife  of  minds  for  he  knew  how  to 


INTRODUCTION  XXIX 

bring  into  the  light  of  day  that  which  was  good  in  the 
most  confused  conceptions. 

"Duclaux  was,  above  all  things,  an  independent.  He 
esteemed  scientific  doctrines  according  to  their  fecundity 
without  believing  them  final  and  thought  usually  that 
the  fruitful  periods  of  science  are  those  wherein  dogmas 
are  shaken.  His  knowledge  was  truly  encyclopaedic  ; 
Duclaux  had  studied  to  the  bottom  the  mathematical  and 
physical  sciences  and  was  quick  to  understand  all  the 
others.  Thus  he  was  capable  of  writing  a  book  like  his 
Traité  de  Microbiologie,  and  of  treating  with  competence 
subjects  pertaining  to  physics  and  to  medicine.  The 
readers  of  these  Annales  have  had  the  proof  many  times 
in  the  critical  reviews  where  he  developed  a  question 
with  remarkable  precision  and  ease.  I  need  Dot  recall 
to  them  the  qualities  of  Duclaux  the  writer.  No  scien- 
tific man  of  his  time  has  written  better  than  he,  no  one 
has  better  employed  his  talent. 

"Duclaux  was  an  incomparable  professor.  His  facility 
of  speech  never  served  to  mask  the  difficulties  of  a  sub- 
ject; he  went  to  the  bottom  of  things  without  fatiguing 
the  attention,  because  with  him  everything  became  easy 
to  understand.  His  lectures  have  determined  more  than 
one  vocation  and  provoked  numerous  investigations. 
He  sowed  ideas  and  rejoiced  to  see  them  germinate  in  the 
fields  of  others. 

"The  regrets  inspired  by  the  loss  of  such  a  man  will  be 
extinguished  only  with  those  who  have  known  him. 
But  the  esteem  and  the  admiration  for  Duclaux  will  be 
durable,  for  his  works  will  be  there  to  attest  that  he  was  a 
scientific  man  of  the  first  order  and,  what  is  much  more 
rare,  a  noble  character." 

I  have  ventured  to  add  to  the  book  a  few  footnotes 
indicating  progress  in  certain  fields  of  research,  an  index, 


XXX  INTRODUCTION 

an  annotated  list  of  persons  mentioned,  a  portrait  of 
Pasteur  made  from  a  bronze  in  my  possession,  several 
from  middle-period  photographs  and  one  from  a  photo- 
graph taken  in  his  old  age.  To  these  I  have  added  two 
portraits  of  Duclaux,  one  from  a  photograph  made  a 
year  or  two  after  he  became  director  of  the  Pasteur 
Institute  (about  1897),  the  other  from  an  admirable  oil 
painting  made  by  Ernest  Bordes  in  the  last  year  of  his 
life  and  purchased  by  the  French  Government  for  the 
Pasteur  Institute,  both  through  the  courtesy  of  Madame 
Duclaux.  For  a  third  portrait  of  Duclaux  the  reader 
may  consult  the  Frontispiece  in  "Bacteria  in  Relation  to 
Plant  Diseases"  Vol.  I,  Carnegie  Institution  of  Washing- 
ton, 1905,  where  also  may  be  found  another  portrait 
of  Pasteur  and  one  of  Roux. 

The  greatest  progress  of  bacteriology  since  this  book 
was  written  has  been  in  the  field  that  would  have  inter- 
ested Pasteur  most,  namely,  in  that  of  immunology, 
which  now  has  its  own  text-books  and  journals.  Read 
in  the  light  of  the  new  knowledge,  the  Eighth  Part  of 
this  book  seems  very  ancient  history  although  it  well 
expresses  the  current  ideas  of  twenty  years  ago  and  will 
always  serve  as  an  important  landmark. 

E.  F.  S. 


EMILE   DUCLAUX 

(From  a  painting  made  during  the  last  year  of  his  life,  by  Ernest 

Bordes.) 


AUTHOR'S  PREFACE 

On  opening  this  volume  someone  will  say:  "How  is  it 
possible  to  make  the  history  of  a  mind?  One  could 
write  an  exact  history  of  a  man:  he  has  spoken,  he  has 
written,  he  has  done  things;  we  know  where  to  lay  hold 
of  him,  and  can  follow  him  and  judge  him.  But  a  mind, 
especially  that  of  a  scientific  man,  is  a  bird  on  the  wing; 
we  see  it  only  when  it  alights,  or  when  it  takes  flight. 
When  it  is  the  mind  of  a  genius,  like  Pasteur,  the  diffi- 
culty seems  almost  insoluble.  We  may,  by  watching 
closely,  keep  it  in  view,  and  point  out  just  where  it 
touches  the  earth.  But  why  does  it  alight  here  and  not 
there?  Why  has  it  taken  this  direction  and  not  that 
in  its  flight  toward  new  discoveries?  If  it  were  possible 
for  you  to  know  this  and  tell  us,  Pasteur  would  no  longer 
be  a  genius,  escaping  analysis;  and  if  you  do  not  tell  us, 
you  will  merely  draw  up  a  report,  not  write  a  history." 

All  this  is  true,  and  nevertheless  I  have  written  this 
book.  I  have  done  so  for  two  reasons:  the  first  is  that 
Pasteur  was  not  a  savant  like  the  others.  His  scientific 
life  had  an  admirable  unity;  it  was  the  logical  and  har- 
monious development  of  one  and  the  same  thought.  Of 
course  he  did  not  know  when  he  made  his  first  studies  in 
crystallography  that  he  would  end  by  discovering  a 
means  of  preventing  rabies.  But  neither  did  Chris- 
topher Columbus  know  when  he  set  forth,  that  he  would 
discover  America.  He  only  divined  that  by  going  always 
in  the  same  direction  he  would  find  something  new.  So 
with  Pasteur.  From  the  beginning  of  his  studies  he  had 
before  him  a  problem  of  life,  and,  having  found  the  road 
to  it,  from  that  time  he  always  traveled  in  the  same  di- 
rection, consulting  the  same  compass.     Without  doubt 

xxxi 


XXX11  AUTHORS    PREFACE 

he  has  traversed  many  different  countries  leaving  foot- 
prints, but  he  did  not  intend  to  explore  them;  they  were 
merely  along  his  pathway  and  the  grandeur  of  his  dis- 
coveries makes  it  possible  for  the  history  of  his  mind, 
even  though  reduced  to  a  report,  to  clothe  these  adven- 
tures with  all  the  air  of  a  romance. 

My  second  reason  is  that  in  its  details  this  scientific 
life  is  no  less  interesting  than  in  its  ensemble.  As  one 
may  readily  conceive,  Pasteur  encountered  many  diffi- 
culties and  many  obstacles.  These  obstacles  we  recog- 
nize more  clearly  as  such,  now  that  they  have  been 
surmounted  and  we  see  them  behind  us.  It  is  interesting 
to  see  how  Pasteur  outflanked  or  evaded  them.  He 
employed  for  that  purpose  qualities  of  the  first  order. 
At  the  same  time  audacious  and  prudent,  deceiving 
himself  sometimes  even  for  a  long  period  but  being 
brought  back  constantly  to  the  true  path  by  that  ex- 
acting experimental  method  of  which  he  has  so  often 
spoken  gratefully,  he  is  always  worthy  of  admiration 
and  worthy  also  to  serve  as  an  example.  It  is  less  for 
the  purpose  of  making  an  eulogy  than  for  purposes  of 
instruction  that  I  have  attempted  to  write  his  history, 
in  which  I  set  aside  all  that  relates  to  the  man,  that  I 
may  speak  only  of  the  savant.  I  have  desired,  in  the 
ensemble  as  well  as  in  the  particulars,  to  give  thege  esis 
of  his  discoveries,  believing  that  he  has  nothing  to  lose 
by  this  analysis,  and  that  we  have  much  to  gain.  But 
I  found  the  task  difficult.  It  is  now  for  the  skeptical 
reader  to  say  whether  I  have  succeeded. 


PASTEUR: 
THE  HISTORY  OF  A  MIND 


PASTEUR 

(At  Thirty.) 


PASTEUR: 
THE  HISTORY  OF  A  MIND 


FIRST  PART 
Works  on  Crystallography 


THE  PREDECESSORS  OF  PASTEUR:  HAÛY,  WEISS, 
DELAFOSSE 

If  we  wish  to  take  exact  account  of  the  progress 
brought  about  in  science  by  the  different  studies  of  Pas- 
teur, the  first  thing  to  do  is  to  become  acquainted  with 
the  state  of  our  knowledge  up  to  the  time  when  each  one 
of  these  studies  advanced  it.  In  order  to  understand 
clearly  the  progress  they  have  made,  we  must  know  from 
what  they  started.  But  that  is  not  as  easy  as  we  might 
think.  To  get  an  idea  of  the  general  intellectual  status 
of  any  period  one  must  not  content  himself  with  reading 
the  classical  books  and  manuals  of  the  epoch:  these 
books  are  always  behind  the  knowledge  of  the  labora- 
tories, that  which  is  in  the  air,  that  which  one  breathes, 
and  which  arouses  investigators.  We  encounter  another 
danger  in  resorting  to  sources  and  original  memoirs; 
viz.,  the  danger  of  taking  the  opinions  and  ideas  of  their 
authors  for  current  opinions  and  ideas.  A  scientific 
man  worthy  of  the  name  is  always  in  advance  of  his  con- 
temporaries :  between  him  and  them  is  a  middle  zone  in 
which  one  must  take  his  stand  in  order  to  judge  the  under- 
takings and  the  progress  of  a  period;  but  where  is  one  to 
find  this  middle  ground,  and  how,  when  he  has  found  it, 

l 


1  pasteur:  the  history  of  a  mind 

is  he  to  see  justly,  that  is  to  say,  to  judge  with  the  judg- 
ment of  that  time?  How  abstract  oneself  from  what  has 
been  learned  since,  and  take  on  again  the  necessary 
ignorance?    $ 

Nevertheless,  I  shall  attempt  to  do  this  throughout 
this  volume;  but,  as  it  is  easy  to  understand,  the  greatest 
difficulties  are  at  the  beginning.  Familiar  as  we  are 
to-day  with  the  theories  of  molecular  structure,  we  have 
some  difficulty  in  picturing  to  ourselves  the  chaotic 
condition  of  these  ideas  among  the  scientific  men  of  1840. 

They  had  a  knowledge  of  the  chemical  molecule. 
They  knew  it  is  formed  by  a  grouping  of  generally  quite 
stable  atoms,  the  number,  weight  and  nature  of  which 
are  ordinarily  very  well  defined.  They  knew,  for  ex- 
ample, that  there  is  one  atom  of  chlorine  and  one  of 
sodium  in  marine  salt,  while  in  calcium  carbonate  there 
is  one  atom  of  calcium,  one  atom  of  carbon,  and  three 
atoms  of  oxygen.  They  had  recognized  that  the  different 
compound  molecules  differentiated  themselves  ordinarily 
by  the  number  and  nature  of  the  atoms  composing  them; 
that  there  are,  nevertheless,  some  which  contain  the  same 
number  of  the  same  atoms  without  being  identical,  from 
which  one  was  led  to  suppose  that  they  were  arranged 
somewhat  differently.  But  in  what  did  these  arrange- 
ments consist?  How  do  the  atoms  dispose  themselves 
in  relation  to  each  other  in  a  molecule?  What  is  the 
resultant  form  for  this  molecule?  These  were  questions 
on  which  no  one  had  clear  ideas. 

Crystallography  had  given  no  answer,  contrary  to 
what  we  might  believe  to-day,  after  the  teachings  which 
this  science  has  furnished  us  It  held  to  Haiiy's  narrow 
and  geometrical  conception  of  the  integral  crystal  mole- 
cule. We  know  that  he  called  by  this  name  the  little 
solid,  the  juxtaposition  and  superposition  of  which  in  an 
infinite  number  resulted  in  the  formation  of  the  crystal. 


THE    PREDECESSORS   OF   PASTEUR 


By  breaking  a  cubic  crystal  of  marine  salt  we  reduce  it 
to  many  little  cubes  which,  pulverized  in  their  turn, 
would  bring  us,  if  it  were  possible  to  push  the  division 
far  enough,  to  the  integral  molecule,  which  also  we  may 
suppose  to  be  a  cube.  By  superposing,  or  placing  in 
juxtaposition  a  sufficiently  large  number  of  these  invisi- 
ble cubes  we  can  form  a  cubic  crystal  of  any  volume 
whatever,  and  this  example  suffices  very  well  to  repre- 
sent to  us  the  integral  molecule  of  Haiiy.  But,  in  the 
mind  of  this  savant,  these  integral  molecules  of  the 
crystal  bore  no  necessary  relation  to  the  chemical  mole- 
cule. In  order  to  make  an  integral  molecule  of  marine 
salt  it  sufficed  that  eight  chemical  molecules,  each  formed 


T~ 79     fp— ^ 


&4 


.-&.-.- 


i> 


FlQ.    1. 


-Diagrams  illustrating 'primitive  conceptions  of  the  distribution  of 
molecules  in  crystals. 


of  one  atom  of  chlorine  and  one  of  sodium,  should  group 
themselves  into  the  form  of  a  cube.  What  these  chem- 
ical molecules,  themselves,  might  be,  spheres  (as  repre- 
sented in  Fig.  1),  cubes,  tetrahedrons,  etc.,  was  a  matter 
of  entire  indifference;  their  form  had  nothing  to  do  with 
it;  it  was  their  grouping  alone  that  determined  the  form 
of  the  integral  molecule  of  the  crystal  and,  consequently, 
that  of  the  crystal  itself. 

This  grouping,  according  to  Haiiy,  was  determined  by 
the  particular  nature  of  the  chemical  molecule  and 
could  only  occur  among  molecules  which  were  similar 
and  completely  identical.  The  geometrical  regularity 
was  evidence  of  the  physical  and  chemical  regularity. 
The  discovery  of  facts  relating  to  isomorphism  came 


4  pasteur:  the  history  of  a  mind 

shortly  to  change  ideas  on  this  point.  By  showing  that 
without  changing  the  form  of  a  crystal  of  calcium  car- 
bonate, Iceland  spar  for  example,  it  was  possible  to  re- 
place as  large  a  number  as  one  wished  of  atoms  of 
calcium  by  an  equal  number  of  atoms  of  magnesium, 
Mitscherlich  introduced,  in  a  form  still  vague,  a  struc- 
tural conception  of  the  crystal  entirely  different  from 
that  of  Haiiy.  If  atoms  of  calcium  and  magnesium  can, 
without  any  change  of  form,  be  substituted  one  for  the 
other  in  a  crystal,  it  is  because  they  are  of  the  same  form, 
or  what  amounts  to  the  same  thing,  because  they  act 
at  a  distance  in  the  same  way.  Thus  the  geometry  of 
the  integral  molecule  was  abandoned  to  approach  the 
geometry  of  the  chemical  molecule,  and  one  could  say 
that  calcium,  magnesium,  iron,  manganese,  and  zinc, 
which  give  carbonates  crystallizing  in  the  same  form  as 
Iceland  spar,  have  atoms  of  the  same  form,  while  baryum 
and  strontium,  which  give  entirely  different  carbonates, 
not  isomorphic  with  the  first,  have  atoms  of  another  form. 
As  in  the  molecules  of  the  carbonates  of  calcium,  of  iron, 
of  magnesium,  of  manganese  and  of  zinc  everything  is 
identical  (except  the  metals,  whose  atoms  are  of  the  same 
form),  it  was  assumed  that  the  chemical  molecules 
of  these  different  bodies  are  also  of  the  same  form,  and 
by  conceiving  that  the  integral  molecules  of  the  different 
crystals  are  also  of  the  same  form,  the  conclusion  was 
reached  that  between  the  crystalline  form  of  any  sub- 
stance whatsoever  and  the  constitution  of  its  chemical 
molecule  a  relation  existed  which,  though  still  vague,  was 
most  certainly  much  closer  than  the  theory  of  Hauy 
assumed  it  to  be. 

Clearly  not  all  of  these  deductions  were  based  on  solid 
foundations,  and  one  could  almost  as  well  have  explained 
these  new  facts  on  the  doctrine  of  Hauy  by  admitting 
that  the  chemical  molecules  of  different  forms  could 


THE    PREDECESSORS    OF    PASTEUR  5 

balance  themselves  at  the  eight  angles  of  a  cube,  and  that 
a  molecule  of  carbonate  of  iron  could  displace  without 
disturbance  at  one  of  these  angles  a  molecule  of  calcium 
carbonate  of  an  entirely  different  configuration.  But 
a  new  theory  in  order  to  be  useful  and  fruitful  does  not 
need  to  have  a  solid  foundation.  It  is  enough  that  it 
should  be  sufficiently  well  founded  to  give  a  new  point 
of  view,  one  which  allows  the  investigator  to  see  things 
the  other  way  around,  and  it  even  happens  that  some 
inexact  theories  may  claim  an  active  part  in  progress. 
The  progress  which  the  very  original  researches  of 
Mitscherlich  brought  about  was  incontestible. 

Some  years  later,  M.  Delafosse,  a  pupil  of  Haiiy, 
studying  another  phenomenon  than  isomorphism,  that 
of  the  hemihedron,  advanced  a  step  farther.  The 
beautiful  geometrical  laws  stated  by  Haiiy  were  some- 
times found  lacking.  They  required,  for  example,  that, 
since  the  eight  angles  of  a  cube  are  identical  from  a 
physical  point  of  view,  every  natural  modification  which 
acts  on  the  one  should  also  act  on  the  other,  for  why 
should  there  be  any  choice?  If  one  of  them  is  inter- 
sected by  a  plane  and  is  truncated,  this  truncation,  what- 
ever it  is,  must  be  repeated  eight  times.  But  it  some- 
times happens  that  only  four  of  the  angles  of  a  cube  bear 
planes,  and  these  are  placed  in  such  a  way  that  no  two 
of  them  are  ever  at  the  extremities  of  the  same  edge  of 
the  cube.  The  ensemble  of  these  four  faces  prolonged  in 
the  imagination  form  a  tetrahedron.  This  is  the  case 
with  boracite  which  crystallizes  in  the  cubic  system. 
Quartz  likewise  forms  hexagonal  prisms  (Fig.  1)  and  the 
twelve  angles  at  its  two  bases  are  physically  identical. 
Nevertheless,  it  often  happens  that  only  six  of  these 
angles,  situated  for  example  alternately  above  and  below 
the  lateral  edges,  are  intersected  by  facets  which,  joined 
together,  would  form  a  rhombohedron  with  six  faces. 


6  pasteur:  the  history  of  a  mind 

One  finds  analogous  facts  in  the  other  systems  of  crystals. 
Whence  come  these  apparent  exceptions  to  that  regular- 
ity which,  really  without  knowing  just  why,  we  attribute 
to  the  laws  of  nature? 

Hauy  was  very  familiar  with  these  phenomena  of  the 
hemihedron  and  if  he  did  not  attribute  to  them  any 
great  importance  it  is  because  his  theory  led  him  to 
a  somewhat  distorted  view  of  them,  as  I  have  just  said. 
According  to  his  conception  the  form  of  the  integral 
molecule  was,  first  of  all,  that  which  cleavage,  the  natural 
division  of  the  crystal,  gave  to  it.  A  cubical  crystal  of 
marine  salt  produces  cubes  by  cleavage;  a  rhombohedral 
crystal  of  Iceland  spar  gives  in  the  same  way  rhombo- 
hedrons.  The  rhombohedron  was,  therefore,  for  Hauy 
a  primitive  form.  When  we  intersect  the  six  lateral 
angles  by  planes  having  the  same  angle  of  inclination 
to  the  faces  of  the  rhombohedron,  we  obtain  by  a 
perfectly  regular  process  of  derivation,  the  hexagonal 
prism  of  quartz.  And  so  for  the  other  cases.  This 
conception  formed  a  logical  and  coherent  whole,  but  left 
Haiiy  indiffèrent  to  the  questions  of  the  hemihedron. 

In  order  to  understand  the  hemihedral  character 
of  the  rhombohedron,  it  is  necessary  to  reverse  the 
order  and  take  the  hexagonal  prism  as  the  primitive 
form.  Then  the  rhombohedron  can  be  derived  from 
it  only  by  way  of  the  hemihedron.  The  same  is  true 
in  the  other  systems.  Weiss,  the  mineralogist,  did 
this  and  straightway  the  hemihedron  appeared  to 
be  a  phenomenon  more  frequent  than  was  supposed, 
and  there  arose  a  problem  requiring  solution.  Why 
this  deviation  from  the  law  of  symmetry? 

This  is  what  Delafosse  tried  to  explain  in  1840, 
by  the  aid  of  a  deceptive  hypothesis  which  to-day 
seems  very  childish.  "In  the  prismatic  quartz,"  he 
said,  "the  hemihedral  constitution  exists  without  being 


BIOT   AND   J.    HERSCHEL  7 

visible  externally,  since  this  prism  can  be  derived  from 
a  rhombohedron.  Some  rhombohedrons  may,  very 
easily,  pile  themselves  up  in  such  a  way  that  they 
form  a  hexagonal  prism.  In  the  same  way  some  tetra- 
hedrons may  so  adjust  themselves  as  to  give  a  cube. 
Therefore,  if  we  admit  that  the  crystalline  net-work 
of  prismatic  quartz  is  formed  of  rhombohedral  mole- 
cules, as  boracite  is  formed  of  tetrahedral  crystals, 
all  difficulty  vanishes  between  Weiss  and  Haiïy:  the 
molecular  polyhedron  will  express  the  dissymmetry 
by  its  form,  but  this  dissymmetry  will  not  necessarily 
appear  in  the  external  aspect  of  the  crystal." 

This  solution  of  the  difficulty  is,  I  repeat  it,  very 
infantile.  It  is  a  pure  invention  and  Delafosse  did 
nothing  to  give  it  a  firmer  foundation  ;  nevertheless  it  made 
for  progress,  by  virtue  of  that  which  I  have  just  pointed 
out,  for  it  introduced  into  the  mind  this  idea  that  the 
form  of  the  integral  molecule  of  the  crystal  is  not  as 
closely  bound  up  as  Hauy  thought  with  the  form  of 
the  crystal  itself.  We  shall  soon  see  the  influence 
of  this  conception  upon  Pasteur,  the  pupil  of  Delafosse, 
and,  like  him,  passionately  fond  of  questions  of  molecu- 
lar structure. 


II 

BIOT  AND  J.  HERSCHEL 

The  general  law,  just  now  stated,  that  a  science  pro- 
gresses above  all  by  changing  its  point  of  view,  explains 
the  aid  which  it  always  derives  from  kindred  sciences; 
and  it  is  especially  because  young  minds  search  most 
eagerly  and  are  more  open  to  these  suggestions  from 
without,  that  youth  is  particularly  the  time  when  the 
spirit  of  invention  flourishes.     In  the  case  with  which 


8  pasteur:  the  history  of  a  mind 

we  are  dealing  the  progress  came  by  way  of  physics 
from  the  introduction  into  the  questions  of  mineralogy 
of    the    power    to   rotate   the   plane    of   polarization. 

We  know  that  every  impression  of  light  is  the  result 
of  a  vibration.  It  is  as  though  a  rigid  rod,  clamped  in  a 
vise  at  one  end,  should  vibrate  at  the  other  end,  oscill- 
ating about  a  position  of  equilibrium.  If,  on  the  moving 
end,  there  is  a  polished  button  making  a  luminous  point, 
we  can  describe  with  this  luminous  point  an  ellipse, 
a  circle,  or  a  straight  line.  Let  us  consider  this  last 
case,the  simplest  one,  and  let  us  call,  for  sake  of  argument, 
the  plane  of  polarization  the  plane  which  contains 
the  vibrating  rod  and  the  luminous  line  which  its 
extremity  describes.  Let  us  suppose  this  plane  verti- 
cal, and  the  luminous  point  moving  before  us  in  the 
line  occupied  by  the  hands  of  a  clock  indicating  six 
o'clock,  i.e.,  in  a  vertical  line.  As  long  as  only  the 
air  intervenes  between  the  luminous  point  and  our 
eye  the  vibration  will  not  change  direction,  but  there  are 
many  transparent  substances  which,  when  traversed 
by  the  vibration,  would  make  it  project  itself  along 
the  lines  of  the  hands  of  a  clock  indicating  five  minutes 
of  five  for  a  certain  thickness  traversed,  or  ten  minutes 
of  four  for  a  thickness  twice  as  great.  In  other  words, 
these  substances  rotate  the  plane  of  polarization  to  the 
left  an  amount  proportional  to  their  thickness.  We 
call  them  substances  having  a  left  rotary  power,  or,  to 
abbreviate,  left-handed  substances.  There  exist,  further- 
more, right-handed  substances,  of  which,  mutatis  mutandis, 
the  definition  is  the  same. 

Crystallized  quartz,  the  hemihedral  form  of  which 
we  have  just  seen,  is  typically  one  of  these  substances 
endowed  with  rotary  power;  it  rotates  the  plane  of 
polarization  of  a  ray  of  light  which  traverses  it  in  the 
direction  of  the  axis,  and  Biot,  in  the  very  careful  study 


BIOT   AND   J.    HEKSCHEL 


which  he  made  of  the  laws  of  this  rotation,  remarked 
that  certain  quartz  crystals,  of  a  definite  thickness,  rotate 
the  plane  of  polarization  as  much  to  the  right  as  other 
quartz  crystals  of  the  same  thickness  turn  it  to  the  left. 
He  summed  up  the  whole  matter  briefly  by  saying  that 
there  are  right-handed  and  left-handed  quartz  crystals. 
But  here  a  curious  circumstance  presented  itself. 
Haiiy  had  observed  at  the  angles  of  his  prismatic  quartz 
crystals  some  hemihedral  facets  (x,  x'  Fig.  2)  different 
from  those  in  the  simple  example  which  we  have  just 


Quartz  plagihedral  left. 


Quartz  plagihedral  right. 


been  considering,  but  which  when  prolonged  would 
still  give  a  rhombohedron.  He  had  also  remarked  that 
these  facets,  which,  in  pursuance  of  symmetry  should 
have  been  doubled  for  each  of  the  angles  which  they  cut, 
were  in  the  majority  of  cases  single,  that  is  to  say  that 
only  one  of  them  was  preserved  and  this  facet  inclined 
according  to  the  crystal,  sometimes  in  one  direction 
sometimes  in  the  other,  to  the  edge  which  bore  it. 
When  the  inclination  was  in  one  direction  with  respect 
to  one  edge  of  the  prism  it  was  in  the  same  direction 
with  respect  to  the  five  other  edges.  He  called  plagi- 
hedrons  all  crystals  which  had  these  hemihedral  facets; 
right-handed  plagihedrons,  those  in  which  these  facets 


10  pasteur:  the  history  of  a  mind 

inclined  to  the  right,  the  crystal  being  oriented  in  a 
manner  agreed  upon;  left-handed  plagihedrons,  those 
in  which  it  inclined  to  the  left.  There  he  rested  the 
matter.  His  pupil,  Delafosse,  had  likewise  seen  in 
these  crystal-facets  only  the  confirmation  of  his  ideas 
respecting  the  tetrahedral  character  of  the  integral  mole- 
cule. If  we  imagine  a  series  of  tetrahedrons,  threaded  end 
to  end  along  a  rigid  rod,  this  thread  will  terminate  at 
one  end  in  a  point,  at  the  other  end  in  a  plane  ;  the  one  ex- 
tremity corresponded,  for  Delafosse,  to  the  corner  which 
was  not  truncated  and  remained  pointed,  the  plane  sur- 
face to  the  other  extremity  bearing  the  hemihedral  facet. 
For  some  years  the  discovery  of  Biot  and  that  of 
Haiiy  existed  side  by  side  in  science  without  influencing 
each  other.  It  was  John  Herschel  who  applied  to 
this  inert  machinery  the  drop  of  oil  destined  to  make  it 
go.  He  bethought  himself  of  combining  the  purely 
crystallographical  observation  of  Haiiy  on  the  right 
and  left-handed  plagihedrons  with  the  purely  physical 
observation  of  Biot  on  the  right-  and  left-handed 
quartz.  Since  one  defines  arbitrarily  the  crystallo- 
graphical position  of  the  crystal  of  quartz  which  he 
examines,  it  is  possible  to  place  the  crystal  in  such  a 
way  that  the  right-handed  quartz  shall  be  also  the  right- 
handed  plagihedron,  and  the  left-handed  quartz,  the 
left-handed  plagihedron.  Thus  there  appeared  to  be 
a  connection  between  the  crystalline  form  and  the  direc- 
tion of  the  rotation.  Observe  that  this  arbitrary 
definition  which  we  have  just  made  is  not  at  all  obliga- 
tory and  may  be  replaced  by  the  opposite  one. 
What  is  essential  is  that  the  existence  of  the  rotary 
power  was  put  by  Herschel  into  relation  with  the 
inequalities  in  construction  of  the  crystal,  and  that 
along  side  of  the  different  but  nevertheless  similar 
structures    which    the    existence    of    the    right-handed 


BIOT  AND   J.    HERSCHEL  11 

and  left-handed  plagihedrons  oblige  us  to  admit  as 
present  in  the  quartz,  we  can  place  the  parallel,  but 
inverse,  actions  which  it  has  on  polarized  light. 

I  have  just  spoken  of  structure.  It  is  necessary 
to  make  here  an  important  remark:  this  action  on 
polarized  light  manifests  itself  only  in  crystallized  quartz. 
With  the  amorphous  quartz,  or  silicia  in  solution 
in  any  liquid  whatsoever,  we  no  longer  find  a  trace  of 
it.  Furthermore,  the  action  takes  place  only  on  a  ray 
of  polarized  light  traversing  the  crystal  in  the  direction  of 
its  longer  axis  and  parallel  to  that  axis,  or  at  least  in  a 
direction  very  little  inclined  away  from  it.  It  dimin- 
ishes rapidly  in  proportion  to  the  augmentation  of  the 
inclination,  and  there  is  no  longer  a  trace  of  it  when 
the  ray  traverses  the  crystal  obliquely  and  in  the  direc- 
tion of  its  shorter  diameter. 

This  circumstance,  which  connected  the  rotary  power 
with  the  molecular  files  of  Delafosse,  was  so  much 
the  more  curious  as  it  did  not  occur  at  all  in  the  other 
substances  in  which  Biot  had  also  discovered  the  rotary 
power.  Almost  all  of  these  substances  were  products  of 
animal  or  vegetable  life:  sugar,  tartaric  acid,  different 
essences,  albumen,  etc.  But  those  which  could  crystal- 
lize, the  sugar  and  the  tartaric  acid,  had  no  polarizing 
action  in  the  crystalline  state.  All,  on  the  contrary, 
when  dissolved  in  water  or  any  liquid  whatsoever,  rotated 
the  plane  of  polarization,  some  to  the  right,  some  to  the 
left.  This  rotation  is  always  the  same  for  the  same  solu- 
tion when  the  density  is  the  same,  regardless  of  the  direc- 
tion in  which  the  light  ray  is  made  to  traverse  the  liquid 
which  is  being  examined,  and  we  can  agitate  this  liquid 
during  the  observation  without  changing  in  any  way  the 
quantity  and  direction  of  the  rotation,  a  fact  which  well 
demonstrates  that  it  does  not  depend  on  the  internal 
arrangement  of  the  active  molecules  in  the  solvent. 


12  pasteur:  the  history  of  a  mind 

This  goes  to  show,  and  Biot  was  well  aware  of  this 
fact,  that  the  action  exerted  by  the  solutions  of  tartaric 
acid  or  of  sugar  is  not  due,  as  in  quartz,  to  the  arrange- 
ment of  the  molecules  in  relation  to  each  other,  that  is  to 
the  form  of  construction,  but  to  the  shape  of  the  molecule 
itself,  a  form  which  must  be  related  to  its  constitution. 

It  is  a  considerable  stride  which  this  conception  forced 
us  to  take.  It  enabled  us  to  attack  a  question  which 
Haiiy  had  neglected  and  which  Delafosse  had  scarcely 
touched — the  question  of  the  form  of  the  molecule.  It 
enabled  us  to  see  in  the  arrangement  of  the  atoms  of  this 
molecule  dissymmetrical  dispositions,  analogous  to  that 
of  the  integral  molecules  of  the  quartz  crystal  in  the 
arrangement  of  the  crystal.  As  to  the  quartz  itself,  it 
had  awakened  ideas,  but  its  importance  diminished  much 
in  comparison  with  substances  which  had  the  rotary 
power  within  the  molecule.  With  the  watches  in  his 
show-case  a  watchmaker  can  make  regular  geometrical 
arrangements  analogous  to  some  of  the  crystalline 
systems;  these  attract  the  eye  and  are  subject  to  certain 
laws,  but  as  soon  as  we  see  that  all  these  watches  are 
going  and  indicating  the  same  hour  we  cease  to  think 
of  the  arrangement  in  the  show-case  and  reflect  rather 
on  the  movement  of  the  watch.  What  connection  could 
there  be  between  the  arrangement  of  the  atoms  in  the 
molecule  and  the  rotary  power? 


Ill 
PASTEUR:  THE  TARTRATES 

Such  was  the  question  which  Pasteur  must  often  have 
put  to  himself,  for  it  was  at  this  juncture  that  he  made 
his  appearance.  Under  Delafosse  he  had  acquired  the 
taste  for  these  researches,  and  as  soon  as  he  was  out  of 


pasteur:  the  tartrates  13 

the  normal  school  and  able  to  enter  the  laboratory  as 
"préparateur,"  he  made  ready  to  pursue  them.  In 
order  to  accustom  the  eye  and  the  hand  to  the  things 
with  which  crystallography  deals,  he  conceived  the  ex- 
cellent idea  of  taking  as  guide  a  rather  extended  treatise 
on  crystalline  forms,  proposing  to  repeat  all  the  experi- 
ments and  all  the  measurements,  and  to  compare  his 
results  with  those  of  the  author  whom  he  followed  step 
by  step.  He  chose  for  this  purpose  a  work  by  Provostaye 
on  the  tartrates,  a  most  fortunate  choice,  for  among  the 
substances  endowed  with  rotary  power,  the  tartrates 
are  those  which  present  in  simplest  form  the  phenomena 
toward  which  the  ambition  of  the  young  savant  directed 
him.  With  other  salts  he  would  have  been  obliged  to 
search  much  longer  to  find  things  not  so  clear,  but  he 
would  have  found  them  in  the  end. 

He  had,  in  fact,  constantly  present  in  his  mind,  this 
correlation  between  hemihedrism  and  the  rotary  power 
discovered  in  quartz.  It  was  useless  to  say  that  it  had 
no  apparent  connection  with  the  case  of  tartaric  acid, 
that  is,  that  it  resided  in  the  arrangement  of  the  mole- 
cules, instead  of  in  the  molecule  itself;  the  ideas  of  his 
master  as  well  as  his  own,  reverting  constantly  to  this 
subject,  told  him  that  there  ought  to  be  something  exter- 
nal indicating  the  mode  of  arrangement  of  the  atoms. 
One  of  the  best  proofs  that  he  searched  for  this  some- 
thing which  his  imagination  had  glimpsed  in  the  memoirs 
of  Biot  and  Herschel,  is  that  he  saw  at  once  on  the 
crystals  of  tartaric  acid  and  the  tartrates  those  hemi- 
hedral  facets  which  neither  Provostaye  nor  Mitscherlich 
had  observed.  The  former,  a  conscientious  worker  but 
without  inspiration  (sans  flamme),  had  certainly  seen 
them  but  he  had  disregarded  them.  The  second,  whose 
fame  is  well  established,  was  occupied  in  his  study  espe- 
cially with  showing  the  isomorphism  of  the  tartrates, 


14  pasteur:  the  history  of  a  mind 

which  have  these  facets,  and  of  the  paratartrates  which 
do  not  have  them.  He  could  not  have  much  considera- 
tion for  these  hemihedral  facets  which  sometimes  upset 
a  parallelism,  otherwise  so  marked.  With  a  slight 
exaggeration  we  may  say  that  Mitscherlich  did  not  wish 
to  see  them  and  did  not  see  them,  while  Pasteur  who 
wished  to  see  them,  saw  them  at  once. 

It  must  be  stated,  however,  that  these  facets  are  not 
always  very  apparent  in  all  the  tartrates  and  in  all  the 
crystals  of  the  same  tartrate,  but  we  can  ordinarily  make 
them  more  manifest  by  changing  slightly  the  conditions 
of  crystallization.  In  short,  as  soon  as  attention  is 
called  to  them  and  we  search  for  them,  we  find  them  in 
all  of  the  tartrates. 

This  confirmed  the  idea  of  a  correlation  between  hemi- 
hedrism  and  the  rotary  power,  but  this  correlation  was 
still  remote.  In  appearance  at  least  not  even  here 
was  there  that  correlation  between  the  position  of  the 
facet  and  the  direction  of  rotation  which  made  the  right- 
handed  quartz  the  right-handed  plagihedron,  and  the 
left-handed  quartz  the  left-handed  plagihedron.  The 
crystals  of  the  different  tartrates  belong  to  different 
systems,  and  have  therefore  very  different  aspects,  and 
we  do  not  find  that  beautiful  harmony  of  forms  which 
makes  almost  twin  brothers  of  the  different  prismatic 
crystals  of  quartz.  The  confirmation  which  Pasteur 
had  just  made  would  have  remained  fruitless  without 
another  discovery  to  give  it  the  life  it  still  lacked,  and 
if  the  first  discovery  belonged  to  the  man  of  reflection 
and  imagination  the  latter  was  due  to  the  experimenter. 

I  have  just  said  that  the  crystals  of  the  different 
tartrates  have  the  most  varied  aspects;  there  are  needles, 
tabular  crystals,  and  prisms;  they  are  more  or  less 
covered  with  facets  which  cut  off  their  angles  or  their 
edges  and  mask  their  primitive  form.     But  in  spite 


pasteur:  the  tartrates 


15 


Fig.  3. — Primitive 
tartrate  crystal. 


of  the  variety  of  their  physiognomy  there  are  some 
features  which  remain  immutable  among  them  and  con- 
stitute their  family  mark.  These  features  are  three 
facets  which  always  succeed  each  other  in  the  same 
order  and  make  between  them  very  nearly  the  same 
angles.  These  facets,  which  consist  in  the  primitive 
form  of  two  contiguous  faces,  P  and  M 
(Fig.  3),  and  a  facet  b1,  cutting  off  the 
intersection  of  the  first  two,  are  parallel 
to  the  same  straight  line  which  might  re- 
place for  us  that  axis  of  the  hexagonal 
prism  of  quartz,  which  has  been  so  useful 
to  us  in  establishing  the  correlation  be- 
tween the  direction  of  the  hemihedrism 
and  that  of  the  rotary  power  in  this 
crystal. 

Let  us  agree  to  place  this  right  line  vertically  in  our 
tartrate  crystals  and  to  turn  forward  the  group  of  three 
facets  which  is  that  characteristic  the  different  crystals 
have  in  common.  All  the  crystals  can  thus  be 
ranged,  in  spite  of  the  variety  of  their  forms,  in  an 
oriented  series  like  soldiers  exhibiting  in  front  the 
same  series  of  buttons.  But  when  one  has  arranged 
them  thus  he  preceives  with  surprise  that  all  of  these 
soldiers  bear  only  one  epaulet,  turned  in  every  case 
in  the  same  direction:  I  mean  to  say  that  all  these  tar- 
trates have  their  hemihedral  facet  inclined  forward  to 
the  right  of  the  observer. 

If  one  turns  them  half-way  around  they  are  like 
children's  lead  soldiers,  or  like  the  god  Janus,  inasmuch 
as  the  front  cannot  be  distinguished  from  the  back: 
the  hemihedral  facet  from  the  rear  is  now  in  front,  but 
it  is  always  to  the  right.  If  one  reverses  them  in  order 
to  observe  them  from  the  other  end  they  resemble 
then  the  double  figures  on  playing  cards;  their  extrem- 


16  pasteur:  the  history  of  a  mind 

ities  resemble  each  other  and  however  one  places 
them,  provided  that  one  puts  in  front  the  characteristic 
group  of  the  three  faces  that  we  have  pointed  out, 
one  of  their  four  hemihedral  facets  comes  again  ob- 
stinately to  take  up  its  position  facing  the  observer, 
and  at  his  right. 

Thus,  a  curious  circumstance,  all  the  tartrates  so 
varied  in  form,  which  Pasteur  had  studied  to  the  number 
of  19,  have  a  rotary  power  in  the  same  direction,  and 
also  a  hemihedrism  in  the  same  direction.  This 
correlation  related  them  to  the  quartz  but  had  a  deeper 
meaning,  for  here  it  could  be  no  longer  a  question  of 
arrangement  of  the  molecules  in  the  crystal,  but  of 
arrangement  of  the  atoms  in  the  molecule.  It  is  clear  that 
one  can  change  the  conventions,  for  example,  examine  the 
crystals  on  the  edge  as  is  the  custom  in  Germany,  instead 
of  on  the  face,  as  is  the  custom  in  France.  In  that  case 
the  hemihedral  facets  incline  to  the  left  when  the  rotary 
power  remains  to  the  right,  but  it  is  the  statement  of  the 
phenomena  which  changes,  and  not  its  nature:  all 
the  tartrates  having  a  rotary  power  in  the  same  direction 
have  also  a  hemihedrism  in  the  same  direction,  and  that 
demonstrates  a  relation  between  the  form  of  the  molecule 
and  its  mode  of  action  on  light. 


IV 
THE  PARATARTRATES 

It  is  evident  that  we  have  made  progress  since  the 
study  on  quartz.  Now  we  find  ourselves  studying  with 
Pasteur  the  manner  of  grouping  of  the  atoms.  And 
here  belongs  an  unforeseen  discovery. 

In  the  factories  where   tartaric   acid  is  made   one 


THE    PARATARTRATES  17 

sometimes  finds  in  the  cavities  between  the  large  crystals 
of    this    acid    some    little  needle-like   crystal  forming 
tufts  which  are  visible  as  an  opaque  white  mass  on  the 
surface  of  the  semitransparent  tartaric  acid  and  some- 
times so  much  resemble  oxalic  acid  crystals  that  in  the 
factory  of  Thann,  where  they  were  formerly  very  abun- 
dant, they  have  been  taken  for  oxalic  acid  crystals  and 
an  attempt  made  to  sell  them  as  such.  It  was  soon 
recognized  that  they  were  formed  of  a  particular  kind 
of  tartaric  acid,  giving  salts  entirely  similar  to  the  tar- 
trates.     Mitscherlich  who  made  a  comparative  study 
of    the    known    tartrates   and    of     these    new    salts, 
which    he    called    paratartrates,  found   them  identical 
in    all  their  relations.       They  had  the  same   crystal- 
line form,  the  same  specific  gravity,  the  same  double 
refraction    in    the    crystalline    state,    the   same  angle 
of  the  optical  axes,  the  same  index  of  refraction  when 
they   were  dissolved  in  the  same  proportion  of  water. 
In  short,  no  method,  either  physical  or  chemical,  made  it 
possible  to  distinguish  them,  and  they  seemed  identical 
in  every  respect,  save  this,  that  the  tartrates  acted  on 
polarized   light   while   the  paratartrates  were   entirely 
without  action. 

Having  arrived  at  this  stage  in  his  researches,  Pasteur 
could  not  fail  to  be  impressed  by  this  apparent  contradic- 
tion. " Mitscherlich  was  deceived,"  he  said,  "in  affirm- 
ing that  the  crystals  of  the  tartrates  and  the  paratartrates 
resemble  each  other.  There  must  be  some  external  differ- 
ences between  them  as  regards  the  hemihedral  facets. 
Mitscherlich,  preoccupied  with  his  ideas  on  isomorphism 
which  made  much  of  all  the  crystalline  resemblances 
between  the  different  forms,  would  not  have  seen  these 
differences  which  he  did  not  seek,  but  I,  who  have  the 
preconceived  idea  of  their  existence,  am  in  a  good  posi- 
tion to  find  them  if  they  are  there." 


18  pasteur:  the  history  of  a  mind 

Experiment,  questioned  in  this  fashion,  gave  an  imme- 
diate response.  All  the  paratartrates  examined  appeared 
with  their  two  epaulets,  that  is  to  say  with  all  the  faces 
required  by  the  laws  of  symmetry:  there  was  no  more 
hemihedrism  :  the  facet  on  the  right  had  its  corresponding 
one  on  the  left  and,  simultaneously,  every  trace  of  action 
on  polarized  light  had  disappeared. 

This  was  a  confirmation  of  Pasteur's  foresight,  a  re- 
ward of  his  daring  intuition.  But,  in  addition  to  this 
foreseen  discovery,  chance,  one  of  those  happy  chances 
which  one  rarely  meets  with  save  when  he  is  constantly 
in  search  of  it,  kept  in  store  an  unexpected  discovery. 
Among  the  paratartrates  there  were  two  which  behaved 
differently  when  they  were  crystallized.  The  others  gave 
crystals  having  hemihedral  facets  in  pairs,  and  conse- 
quently had  no  hemihedrism,  just  as  he- is  no  longer  one- 
armed  who  has  two  arms.  On  the  contrary,  the  double 
paratartrates  of  soda  and  ammonia  on  the  one  hand,  of 
soda  and  potash  on  the  other,  deposit  in  their  mother 
liquors  crystals  which  are  all  hemihedrons,  all  one-armed; 
only  there  are  some  of  them  which  have  the  right  arm, 
and  others  the  left. 

What  did  this  mean?  If  one  regarded  these  facts  as 
a  whole,  the  result  was  confusing,  since  it  showed  the 
apparition  of  hemihedrism  where  there  was  no  rotary 
power.  But  Pasteur  had  advanced  too  far  to  go  back. 
He  had  already  derived  too  much  advantage  from  his 
conception  to  lose  confidence.  "In  spite  of  all  that  was 
unexpected  in  this  result,"  said  he,1  "I  followed  none 
the  less  my  idea.  I  separated  with  care  the  right  and  left- 
handed  hemihedral  crystals  and  observed  separately 
their  solutions  in  the  polarization  apparatus.  Then, 
with  no  less  surprise  than  joy,  I  saw  that  the  right- 

1  Recherches  sur  la  dissymétrie  moléculaire.  Leçon  professée  à  la 
Société  chimique  de  Paris,  1860,  p.  29. 


THE    PARATARTRATES  19 

handed  hemihedral  crystals  turned  to  the  right  and  the 
left-handed  ones  to  the  left  the  plane  of  polarization,  and 
when  I  took  equal  weights  of  each  of  these  kinds  of  crys- 
tals the  mixed  solution  was  neutral  to  polarized  light 
because  of  the  neutralization  of  the  two  equal  and  oppo- 
site individual  deviations." 

We  can  understand  how  in  the  presence  of  this  un- 
expected phenomenon,  with  its  almost  dazzling  confirma- 
tion of  his  preconceived  idea,  Pasteur  received  such  a 
shock  that  he  quitted  the  laboratory,  incapable  of  again 
applying  his  eye  to  the  polariscope.  This  was  a  clear 
ray  of  sunlight  coming  to  illuminate  perspectives  which 
he  had  thus  far  examined  only  in  shadow  or  half  light. 
Now  that  they  were  suddenly  illuminated  it  was  not  the 
time  to  abandon  them. 

The  more  so  as  immediately  there  was  a  harvest  to  be 
reaped.  In  removing  chemically  from  the  right-handed 
hemihedral  crystals  the  tartaric  acid  which  they  con- 
tained, he  found  an  acid  which,  when  compared  minutely 
with  the  acid  of  the  grape,  was  found  to  be  absolutely 
identical  with  it.  The  left-handed  crystals  furnished 
him  furthermore  a  tartaric  acid  also  identical  in  every 
respect  with  the  acid  of  the  grape,  save  in  one  point, 
that  is  that  it  bore  on  the  left  the  hemihedral  facet  which 
the  first  bore  on  the  right,  and  that  its  solutions  deviated 
to  the  left  exactly  the  same  amount  as  equally  concen- 
trated solutions  of  the  tartaric  acid  of  the  grape  deviated 
to  the  right.  When  these  solutions  were  mixed  there 
was  no  deviation,  and  one  obtained  a  third  tartaric  acid, 
the  paratartaric  acid  inactive  by  compensation.  Fur- 
thermore, this  acid  did  not  result  from  a  juxtaposition 
of  these  two  constituents  but  from  their  combination, 
for  properly  concentrated  solutions  of  right-handed  and 
of  left-handed  tartaric  acids  often  give  off  much  heat 
when  mixed,  and  the  liquid  solidifies  on  the  spot  with  an 


20  pasteur:  the  history  op  a  mind 

abundant  crystallization  of  a  paratartaric  acid  identical 
with  the  acid  of  Thann  with  which  we  set  out. 

To  summarize,  there  existed  three  tartaric  acids  iden- 
tical from  the  point  of  view  of  all  their  physical  and  chem- 
ical properties,  save  this,  that  they  each  had  their 
special  hemihedral  facets  and  the  corresponding  rotary 
power.  These  differences  persisted  in  all  their  com- 
pounds and  formed  a  part  of  their  true  nature.  They 
formed  their  distinctive  marks,  which  were  permanent 
and  deep. 


V 

ASPARTATES  AND  MALATES 

This  harmonious  development  from  a  single  fertile 
idea  will  become  still  more  thrilling  presently  when  we 
go  back,  as  we  are  justified  in  doing,  to  the  chemical 
molecule  from  which  comes  the  initial  influence.  For 
the  moment  we  must  ask  ourselves  whether  we  are  here 
in  the  presence  of  a  general  or  an  exceptional  fact.  Do 
all  these  different  organic  substances,  which  Biot  found 
endowed  with  rotary  power,  present  hemihedral  forms 
when  crystallized?  Unfortunately,  not  many  of  them 
give  measurable  crystals  :  asparagin  and  its  different  de- 
rivatives, aspartic  acid  and  malic  acid  do,  however, 
and  Pasteur  made  haste  to  study  them.1 

Asparagin  was  at  this  time  a  rare  substance.  Pasteur 
was  obliged  to  plant  vetch  in  the  garden  and  cellars  of 
the  Academy  of  Strasbourg.  By  known  processes,  from 
the  juice  of  these  plants  he  extracted  the  asparagin  which 
he  crystallized  and  which  he  showed  at  the  same  time 
to  be  provided  with  hemihedral  facets  and  endowed  with 

1  Mémoire  sur  les  acides  aspartique  et  malique.  Ann.  de  ch.  et  de 
phys.,  3e  p.,  t.XXXIV. 


ASPARTATES   AND   MALATES  21 

rotary  power.  Like  the  tartaric  acid  it  carries  over  this 
last  property  into  its  solutions,  whether  acid  or  alkalin, 
but  it  presents  this  unforeseen  peculiarity  of  rotating  to 
the  left  the  plane  of  polarization  when  it  is  in  a  neutral 
or  an  alkalin  solution,  and  on  the  contrary  of  rotating 
it  to  the  right,  and  to  a  much  greater  extent,  when  it  is 
in  an  acid  solution.  In  no  case,  however,  has  it  ceased 
to  be  asparagin  unless  the  liquid  has  been  heated  or 
the  acids  or  alkalies  have  been  too  concentrated,  and  it 
is  possible  by  precipitation  to  recover  it  with  all  the  old 
properties.  This  proved  that  the  rotary  power  of  a 
substance  did  not  depend  on  itself  alone  and  that  if  the 
existence  of  this  power  had  any  significance  for  the  ideas 
on  which  Pasteur  had  taken  his  stand,  its  meaning  and 
importance  were  contingent  and  of  a  secondary  order. 

I  have  just  said  that,  in  order  to  leave  intact  the  as- 
paragin on  which  one  is  working,  it  is  necessary  not  to 
heat  the  liquids.  Boiled  with  an  alkalin  solution,  it  is 
transformed  into  aspartic  acid.  Does  this  acid  keep 
any  of  the  rotary  power  of  the  asparagin?  It  is  too  little 
soluble  in  water  to  make  it  possible  to  study  it  in  aqueous 
solutions.  In  solution  in  the  alkalies  it  rotates  to  the 
left:  in  chlorhydric  or  nitric  acid  it  rotates  to  the  right. 

Another  derivative  of  asparagin  was  still  more  interest- 
ing to  study;  viz.,  the  malic  acid  which  one  can  obtain 
from  it  by  action  of  hyponitric  acid.  This  malic  acid 
accompanies  tartaric  acid  in  the  grape  and  therefore 
should  arouse  curiosity.  Experiment  shows  that  in 
regard  to  the  rotary  power  it  behaves  a  little  like  tartaric 
acid,  and  that  it  sometimes  even  recalls  it  so  much  in  its 
properties  that  one  is  tempted  to  suppose  for  the  two 
acids  origin  from  a  common  atomic  grouping.  Never- 
theless, in  their  ensemble,  the  phenomena  presented  by 
malic  acid  and  the  malates  are  more  complicated  than 
those  of  tartaric  acid  and  the  tartrates.     In  the  latter 


22  pasteur:  the  history  of  a  mind 

we  have  several  series  of  well-ordered  crystals  in  which 
the  correlation  between  the  two  hemihedrisms  and  the 
direction  of  the  rotary  power  is  always  clear.  In  the 
malates,  on  the  contrary,  the  inclination  of  the  facets 
and  the  direction  of  the  rotation  are  sometimes  contrary, 
and  thus  there  disappears,  apparently  at  least,  this  beauti- 
ful harmony  which  had  so  charmed  us  in  the  tartrates. 

If  Pasteur  had  commenced  with  malic  acid  he  would 
have  needed  all  his  perseverance  in  order  to  disentangle 
himself  from  the  midst  of  so  many  contradictory  facts. 
But  at  the  point  which  he  had  reached  his  ideas  were  too 
well  grounded  and  his  experience  already  too  great  for 
him  to  be  astounded  by  these  particular  variations  in  the 
direction  of  rotation  of  the  malates.  He  had  discovered 
quite  parallel  phenomena  in  asparagin,  which  neverthe- 
less remained  always  the  same,  and  also  in  the  aspartates. 
He  had  even  found  examples  of  it  in  the  tartrates,  for 
the  left-handed  calcium  tartrate  dissolved  in  chlorhydric 
acid  gives  a  rotation  to  the  right. 

It  is  under  conditions  like  these,  where  the  judgment  is 
wavering,  that  the  discernment  of  the  scientific  man 
reveals  itself.  Without  being  embarrassed  by  the 
differences  between  the  malates  and  the  tartrates,  he 
saw  and  aimed  at  one  thing  only,  the  resemblances  which 
he  had  perceived  and  pointed  out,  and  he  concluded  with 
a  fine  tranquillity  that  if  there  was  a  common  atomic 
grouping  between  the  right-handed  tartaric  acid  of  the 
grape  and  the  malic  acid  of  the  sorb-tree,  there  must 
also  occur  a  common  atomic  grouping  between  the  left- 
handed  tartaric  acid  and  a  malic  acid  still  unknown, 
which  would  be  the  left  of  the  malic  acid  of  the  sorb-tree. 
And  thus  little  by  little  was  born  in  his  hands  that  science 
of  the  arrangement  of  atoms  which  has  since  attained  so 
much  importance.  Wherever  he  went  Pasteur  was  an 
initiator. 


MOLECULAR   DISSYMMETRY 


23 


Before  leaving  this  subject  let  us  point  out  a  last  series 
of  facts  and  conclusions.  Tartaric  acid  and  malic  acid 
undergo  changes  due  to  the  action  of  heat;  the  former 
gives  pyrotartaric  acid,  the  second  maleic  acid  and  a  fum- 
aric  acid  identical  with  that  which  is  derived  from  the 
fumitory.  Is  the  atomic  grouping  which  gives  to  the 
tartaric  and  malic  acids  the  property  of  acting  on  polar- 
ized light  preserved  intact  in  their  derivatives?  Experi- 
ment shows  that  this  is  not  the  case.  All  these  acids, 
pyrotartaric,  maleic,  fumaric,  and  their  salts  are  inactive. 
According  to  Pasteur's  interpretation,  the  molecules  of 
tartaric  acid,  aspartic  acid  and  malic  acid,  are  dissym- 
metrical; those  of  the  pyrotartaric,  maleic,  and  fumaric 
acids  are  not:  the  atoms  are  differently  grouped  and  a 
new  proof  is  this,  that  the  two  tartaric  acids,  the  right 
and  the  left-handed,  give  only  a  single  pyrotartaric  acid. 


VI 

MOLECULAR  DISSYMMETRY 

The  moment  has  come  to  pursue  more  closely  than 
we  have  hitherto   done   these  ideas   of    dissymmetry. 


ct- 


Fio.  4. — Diagrams  illustrating  molecular  dissymmetry. 

There  is  a  fundamental  difference  between  the  hemihedral 
forms  coming  from  the  cube,  as  in  boracite,  or  from 
the  hexagonal  prism,  as  in  Iceland  spar,  and  the 
hemihedral  forms  realized   in  the   tartrates.     All   the 


24 


pasteur:  the  history  of  a  mind 


Fig.  5. 
Right  tartrate.       ;;    Left  tartrate 


tetrahedons  which  can  be  derived  from  a  cube  by 
hemihedrism  are  identical  and  could  fit  into  one  another. 
The  two  tetrahedrons  represented  in  Fig.  4,  passing 
through  opposite  vertices  of  the  cube,  have  the  same 
angles  and  edges;  it  is  only  necessary  to  reverse  the 
first  in  order  to  make  it  fit  over  the  second  :  they  are 
superposable,  to  speak  in  geometrical  parlance.  The 
same  thing  is  true  for  the  different  rhombohedrons 
derived  from  the  hexagonal  prism.     It  is  quite  otherwise 

for  the  hemihedrons  of  the 
tartrates.  The  tetrahedron 
which  one  obtains  by  pro- 
longing and  joining  the  hemi- 
hedral  facets  which  a  right- 
handed  crystal  of  tartrate 
bears,  is  not  superposable  on 
the  tetrahedron  obtained  in 
the  same  way  from  the  left- 
handed  tartrate.  Their  faces,  it  is  true,  are  equal  two  by 
two,  but  they  are  not  arranged  in  the  same  order  in  re- 
spect to  the  vertices. 

Fundamentally,  the  difference  amounts  to  this,  that 
the  tetrahedron  of  the  cube  has  several  planes  of 
symmetry,  to  the  right  and  left  of  which  the  elements 
are  regularly  distributed.  If  one  imagines  a  reflect- 
ing surface  passing  through  any  given  edge  of  the 
tetrahedron  and  the  center  of  the  opposite  edge,  the 
image  of  the  rear  half  in  this  mirror  coincides  with  that 
of  the  forward  half,  and  inversely:  in  more  general 
terms,  the  object  is  superposable  on  its  image  in  a  mirror. 
We  shall  say  that  in  this  case  there  is  superposable 
hemihedrism.  The  hemihedrism  of  the  tartrates  gives, 
on  the  contrary,  tetrahedrons  which  have  no  plane 
of  symmetry,  which  are  not  superposable  on  their  image, 
and  when  we  reflect  upon  it  we  see  that  "all  material 


MOLECULAR   DISSYMMETRY 


25 


objects,  whatever  they  may  be,  regarded  with  respect 
to  their  form,  or  the  repetition  of  their  identical  parts, 
resemble  the  tetrahedrons  which  we  have  just  distin- 
guished. Some  placed  before  a  mirror,  give  an  image 
which  is  superposable  on  them;  others  do  not,  although 
the  image  reproduces  them  faithfully  in  all  details. 
A  straight  stairway,  a  branch  with  opposite  leaves,  a  cube, 
the  human  body,  all  these  are  objects  belonging  to  the 
first  category.  A  spiral  staircase,  a  branch  with  leaves 
in  a  spiral,  a  screw,  a  hand,  an  irregular  tetrahedron 
are  forms  of  the  second  group.  These  latter  have  no 
plane  of  symmetry."1 

Of  all  these  comparisons  that  of  the  hand  is  the  most 


right. 


Fig.  6. — Tartaric  acids. 

primitive  form. 

c.  Hemihedral  facets. 


left. 


convenient  and  striking.  The  two  hands  are  not  super- 
posable and  one  cannot  put  the  right  glove  on  the  left 
hand,  nor  inversely.  On  the  contrary  the  image  of  a  right 
hand  in  the  mirror  gives  a  left  hand.  Well!  The  two 
hemihedral  tetrahedrons  of  the  right-  and  left-handed 
tartrates  are  like  the  two  hands  :  they  are  not  super- 
posable nor  is  either  superposable  on  its  image,  but 
each  of  them  is  superposable  on  the  image  of  the  other 
in  a  mirror  (Figs.  5  and  6). 

Let  us  recall  now  that  we  were  led  a  moment  since 
to  attribute  forms  of  dissymmetry  connected  with  the 
non-superposable     hemihedrism     of     crystals     to     the 

1  De  la  dissymétrie  moléculaire  des  produits  organiques  naturels. 
Leçon  professée  devant  la  Société  chimique  de  Paris,  1860. 


26  pasteur:  the  history  of  a  mind 

arrangement  of  the  atoms  in  the  molecule,  and  thus 
we  come  quite  naturally  to  represent  to  ourselves  the 
molecules  of  the  two  tartaric  acids,  the  right-  and  the 
left-handed,  not  only  as  dissymmetrical  individually  and 
with  a  non-superposable  dissymmetry,  but  also  as 
having  an  inverse  dissymmetry  one  with  the  other.  If 
one  is  a  right  hand  the  other  is  a  left  hand.  If  one  is  a 
corkscrew  with  a  dextrorse  spiral,  the  other  is  a  corkscrew 
with  a  sinistrorse  spiral.  In  short,  we  know  nothing 
and  we  shall  know  nothing  probably  for  a  long  time  of 
the  mode  of  arrangement  of  the  atoms  in  these  two 
molecules,  but  we  remain  faithful  to  logic  and  the  laws 
of  induction  in  acknowledging  that  these  two  arrange- 
ments, individually,  dissymmetrical,  are  reciprocally  sym- 
metrical in  relation  to  a  plane. 

Once  this  conception  is  admitted,  we  can  easily 
represent  to  ourselves  the  effect  of  these  groupings  in  a 
water  solution  on  a  ray  of  polarized  light  which  trav- 
erses it.  Let  us  suppose  that  this  solution  contains  only 
identical  and  superposable  tetrahedrons,  for  example 
those  of  boracite:  these  molecules  are  present  in  very 
great  numbers  in  the  path  of  the  ray,  even  when 
the  solution  is  not  of  much  thickness;  they  occupy,  in  the 
medium  in  which  they  are  free,  all  possible  positions. 
Consequently,  if  we  suppose  that  one  of  them  is  inclined 
in  a  certain  direction  with  regard  to  the  ray  of  light  and 
acts  on  it  in  a  given  direction,  there  will  always  be 
another  one,  identical  with  it  and  in  the  inverse  position, 
which  will  produce  an  effect  in  the  opposite  direction. 
The  molecular  effects  will  always  counterbalance  there- 
fore in  pairs,  that  is  to  say,  the  light  ray  will  leave 
the  solution  just  as  it  entered  it,  except  for  the  small 
amount  of  absorption  undergone  in  traversing  it.  If,  on 
the  contrary,  the  tetrahedrons  in  solution  are  not 
identical,  if  they  cannot  be  superposed,  it  would  be 


MOLECULAR   DISSYMMETRY  27 

only  in  very  exceptional  positions  that  compensa- 
tions like  those  which  we  have  just  pointed  out 
could  occur,  and,  without  being  able  to  indicate  in 
detail  the  results  or  the  direction  of  the  general  resultant, 
we  see,  nevertheless,  that  the  total  effect  could  not  be 
the  same  as  in  the  first  case.  The  path  of  the  ray  of 
polarized  light  where  the  direction  of  the  vibration 
is  constant  and  unique  must  depend  on  the  direction 
in  which  the  obstacles  it  encounters  are  placed.  With 
out  going  into  this  problem  further,  it  is  possible  to  admit 
that  the  deviation  of  the  plane  of  polarization  depends 
on  the  manner  of  distribution  of  the  obstacles,  and  that, 
according  as  the  dissymmetry  in  the  atoms  is  right  or 
left  there  will  be  a  right  or  a  left  rotation. 

Of  less  importance  is  the  mechanism  of  the  action, 
which  always  remains  a  little  hypothetical.  It  is  suffi- 
cient that  the  experimental  study  of  the  tartrates  has 
linked  indissolubly  these  two  ideas  :  the  molecular  rotary 
power,  and  the  dissymmetry  of  the  molecule.  This 
suffices  to  give  us  the  right  to  attribute  dissymmetrical 
molecules  to  all  substances  acting  in  solution  on  polar- 
ized light,  and  when  one  considers  that  all  these  sub- 
stances belong  to  the  vegetable  or  animal  kingdom, 
that  is  to  say,  are  the  products  of  cellular  activity, 
this  peculiarity  of  structure  becomes  curious,  if  regarded 
closely.  Guided  by  an  imagination  at  once  so  adven- 
turous and  so  well  controlled  as  was  that  of  Pasteur, 
we  are  constantly  on  the  border  of  new  countries,  but  we 
journey  with  security.     . 


28  pasteur:  the  history  of  a  mind 

VII 
DISSYMMETRY  OF  CELLULAR  LIFE 

The  plant,  which  is  the  great  creator  of  organic  matter 
on  the  surface  of  the  globe,  is  an  organism  continually 
engaged  in  the  work  of  synthesis.  By  the  aid  of  sub- 
stances of  the  highest  degree  of  chemical  simplicity, 
carbonic  acid,  water  and  ammonia,  it  manufactures  sub- 
stances more  and  more  complex,  which  it  stores  in  the 
new  tissues  that  it  forms  according  to  its  needs.  As 
soon  as  these  substances  attain  a  certain  degree  of  com- 
plexity we  see  appearing  in  them  the  molecular  rotary 
power,  absent  up  to  that  time.  Carbonic  acid,  oxalic 
acid,  acetic  acid,  ammonia,  urea  and  glycocol,  are  with- 
out action  on  polarized  light:  the  sugars,  tartaric,  malic 
and  citric  acids,  cellulose,  the  gums,  and  the  albuminoid 
substances  are  active. 

At  the  time  when  Pasteur  made  these  studies  the  chem- 
istry of  synthesis  was  still  little  advanced  :  Berthelot  was 
just  beginning  his  work.  But  organic  chemistry  was  in 
full  swing,  and  inorganic  chemistry  was  leaving  the 
hands  of  Berzélius  and  Wohler  to  fall  into  those  of 
Sainte-Claire  Deville.  Already,  at  this  time,  Pasteur 
was  in  position  to  remark  that,  contrary  to  the  majority 
of  natural  organic  products,  all  the  artificial  products 
of  the  laboratories  and  all  the  mineral  species  met  with 
in  nature  were  without  action  on  polarized  light,  that  is 
to  say  they  possessed  a  superposable  image.  Quartz 
itself  is  not  an  exception,  for,  as  we  have  seen,  it  is  only 
the  arrangement  of  the  molecules  in  the  crystal  which  is 
dissymmetrical.  Individually  these  molecules  are  with- 
out action  on  polarized  light.  In  the  same  way  one  can 
arrange  cubes  of  wood,  which  are  exactly  alike,  so  as  to 
make  a  winding  and   dissymmetrical  staircase;  there 


DISSYMMETRY   OF   CELLULAR   LIFE  29 

is  dissymmetry  of  construction  but  not  molecular 
dissymmetry. 

One  could  put  in  the  same  category  as  quartz  other 
minerals  or  salts,  such  as  sulphate  of  magnesium  and 
formate  of  strontium,  substances  having  crystals  with 
hemihedral  facets  but  the  solutions  of  which  are  not  ac- 
tive. In  short,  no  product  of  inorganic  nature  or  of  the 
chemistry  of  the  laboratory  deviates  the  plane  of  polar- 
ization of  light  when  in  solution;  it  is  only  the  products 
of  living  nature  which  have  this  property  but  they  possess 
it  to  a  very  marked  degree  and  carry  it  with  them  when 
they  enter  into  combination  with  other  substances. 

Since  then,  the  chemistry  of  synthesis  has  made 
progress,  and  today,  starting,  like  the  plant,  with  water, 
carbonic  acid  and  ammonia,  and  putting  into  play  only 
the  forces  and  ordinary  resources  of  the  laboratory,  we 
are  able  to  manufacture  artificially  the  majority  of  the 
natural  organic  products.  Is  it  necessary,  therefore,  to 
change  some  of  the  conclusions  which  Pasteur  announced 
in  1850?  Yes,  one  thing  only  which  he  did  not  foresee. 
We  are  able  now,  by  the  aid  of  primitively  inactive  bodies 
to  manufacture  active  ones,  to  thus  produce  dissym- 
metry and  the  rotary  power  in  the  molecule  which  we 
construct.  With  inactive  succinic  acid  we  can  ascend, 
for  example,  to  tartaric  acid.  But  when  a  chemist 
manufactures  thus  artificially  the  right-handed  tartaric 
acid  he  makes  also  necessarily  and  simultaneously  the 
left-handed  form,  so  that  the  combination  which  comes 
from  his  hands  is  inactive.  Nature  alone  has  the  secret 
of  manufacturing  one  without  producing  the  other.  In 
the  grape,  for  example,  she  gives  us  commonly  the  right- 
handed  tartaric  acid  and  not  the  left,  or  at  least  rarely 
the  left,  since  paratartaric  acid,  the  combination  of  the 
right  and  the  left,  sufficiently  abundant  at  one  time  to 
obstruct  the  works  at  Thann,  has  almost  disappeared 


30  pasteur:  the  history  of  a  mind 

there  today,  as  well  as  from  the  other  tartaric  acid 
factories. 

What  is  the  mechanism  of  this  production  of  a  right- 
handed  substance  without  a  trace  of  the  left-handed  one, 
or  inversely?  Are  the  two  forms  produced  simultan- 
eously and  is  one  of  them  utilized  and  consumed  in 
proportion  to  its  production?  In  this  case  nature  would 
behave  like  a  chemist  who,  after  having  formed  at  the 
same  time  the  two  inverse  substances,  should  separate 
them  and  cast  aside  one  of  them  in  order  to  preserve  the 
other.  Some  facts  which  we  shall  soon  encounter  are  in 
accord  with  this  view.  Pasteur  adopted  another  view 
which,  however,  is  not  exclusive  of  the  first.  Possessed 
as  he  was  by  this  novel  idea  of  dissymmetry,  he  boldly 
connected  the  dissymmetry  of  natural  products  with  the 
dissymmetry  of  their  source.  The  earth  is  round,  it  is 
true,  but,  he  thought,  it  is  only  when  in  a  state  of  repose 
that  it  is  symmetrical  and  superposable  on  itself.  As 
soon  as  it  turns  on  its  axis  its  image  in  a  glass  no  longer 
resembles  it,  for  that  turns  in  a  different  direction.  The 
sun's  rays,  which  strike  and  animate  a  leaf  of  a  plant, 
no  longer  have  the  same  direction  in  the  earth  and  in  its 
image.  If  there  is  an  electric  current  circulating  in  the 
direction  of  the  equator  and  presiding  over  the  distribu- 
tion of  magnetism,  this  current  turns  also  in  opposite 
directions  in  the  earth  and  its  image  in  the  mirror.  In 
short,  the  earth  is  a  dissymmetrical  whole  from  the  point 
of  view  of  the  forces  which  make  it  live,  it  and  all  that  it 
produces,  and  it  is  on  this  account  that,  as  soon  as  they 
have  exceeded  a  certain  degree  of  complexity,  the  sub- 
stances which  the  earth's  living  creatures  produce  are 
dissymmetrical  and  endowed  with  a  rotary  power. 

With  this  idea  in  mind,  Pasteur  had  tried  to  crystallize 
the  tartrates  in  the  presence  of  dissymmetrical  forces, 
for  example,  the  poles  of  a  magnet,  and  to  make  a  plant 


DISSYMMETEY   OF   CELLULAE   LIFE  31 

push  out  shoots  by  changing  the  direction  of  the  light 
rays  which  struck  it.  These  attempts  gave  nothing, 
either  to  him  or  to  those  after  him.  But  it  is  possible 
that,  repeated  with  greater  persistence  and  with  more 
powerful  means,  they  would  result  in  something,  and 
that  this  something  would  be  so  remarkable  that  it 
would  pay  for  all  the  trouble  taken  to  produce  it.  We 
cannot  justly  scorn  any  of  these  ideas  of  Pasteur  when 
we  see  how  fruitful  have  been  all  those  which  he  pursued. 


VIII 

SUBSTANCES  INACTIVE  THROUGH  LOSS  OF 
DISSYMMETRY 

We  are  going  to  discover  a  new  proof  of  the  certainty 
of  Pasteur's  intuition.  Starting  with  asparagin,  and 
profiting  by  the  labors  of  Piria,  we  have  seen  that  we 
can  obtain  products  more  and  more  simplified:  aspartic 
acid,  malic  acid,  maleic  acid,  and  fumaric  acid.  In 
this  continued  degradation  of  the  asparagin  molecule 
there  is  a  point  reached  where  the  molecular  dissym- 
metry disappears,  permanently:  this  is  at  the  maleic 
or  fumaric  acid  boundary.  But  it  happened  in  1850 
that  M.  Dessaignes,  an  able  chemist  of  Vendôme, 
succeeded  in  following  inversely  the  steps  of  Piria,  and 
of  remounting  by  the  chemical  path  from  malic  acid 
to  aspartic  acid,  then,  some  months  later,  from  fumaric 
and  maleic  acids  to  the  same  aspartic  acid. 

The  passage  from  malic  acid  to  aspartic  acid  had  not 
surprised  Pasteur,  both  of  them  being  active  on  polarized 
light,  but  the  case  was  different  with  maleic  acid.  In 
transforming  this  into  malic  or  aspartic  acid,  Dessaignes 
would  have  created  an  active  molecule  by  a  laboratory 
operation.  This  would  have  been,  in  the  eyes  of  Pasteur, 
a  great  discovery.  He  must  assure  himself  of  the  truth 
of  it  at  once. 

Pasteur,  therefore,  hastened  to  Vendôme  to  state  his 
scruples  to  Dessaignes,  and  obtained  from  him  without 
difficulty  a  sample  of  the  new  aspartic  acid  which  he  made 
haste  to  study.  As  he  had  expected,  he  did  not  find 
any  rotary  power:  this  acid  was  an  inactive  acid.  But 
it  resembled  so  much,  in  all  its  physical  and  chemical 

32 


SUBSTANCES  INACTIVE  THROUGH  LOSS  OP  DISSYMMETRY  33 

properties,  the  acid  derived  from  asparagin,  that  Des- 
saignes,  who  had  no  preconceived  idea  to  put  him  on 
his  guard,  was  very  excusable  for  having  confused  the 
two. 

This  synthetic  aspartic  acid  is  especially  interesting  in 
that  it  can  be  transformed  into  malic  acid  by  the  methods 
of  Piria,  and  we  may  well  believe  that  Pasteur  was 
curious  to  know  what  malic  acid  one  would  obtain  with  it. 
Experiment  shows  that  we  obtain  a  malic  acid  identical 
with  the  natural  acid,  save  that  it  is  inactive  on  polarized 
light,  as  are  also  its  salts.  This  is  not  all;  the  field 
grows  more  fertile  as  we  cultivate  it.  The  active  malic 
acid  of  the  sorb-tree  or  of  the  grape  corresponds  to  one 
of  the  active  tartaric  acids.  To  what  was  this  new  malic 
acid  comparable?  To  the  paratartaric  acid  inactive  by 
compensation?  Pasteur  had,  against  this  interpretation, 
an  objection  which  is  no  longer  valid.  "  Dessaignes, 
the  father  of  this  malic  acid,  would"  he  thought,  "in 
this  case  have  created  two  molecules  endowed  with 
rotary  power  at  the  expense  of  one  inactive  molecule, 
but  it  is  impossible  to  create  a  single  active  molecule,  to 
say  nothing  of  two."  We  know  today,  not  only  that 
the  thing  is  possible,  but  that  it  has  been  realized. 
It  is  very  probable,  if  not  absolutely  demonstrated, 
that  the  aspartic  acid  manufactured  by  Dessaignes  was 
a  combination  of  the  right-  and  left-handed  acids.  It 
is  certain  that  the  malic  acid  which  Pasteur  had  had  in 
his  hands  was  also  a  paratartaric  acid.  This  error  at 
the  outset  vitiated  the  memoir  which  Pasteur  had 
devoted  to  comparing  the  aspartates  and  malates  with 
each  other  and  with  the  tartrates.  The  majority  of 
the  deductions  which  he  had  drawn  from  these  compari- 
sons are  inexact,  and  must  be  abandoned.  But  there 
are  some  which  survive  and  which  we  should  note. 
Even  in  the  early  years  of  his  life  as  savant,  Pasteur 


34  pasteur:  the  history  of  a  mind 

always  had  the  good  fortune  never  to  wander  very- 
far  from  the  right  path.  His  adventurous  spirit  led 
him  sometimes  to  the  right  or  to  the  left  of  it,  as  he 
followed  the  trail,  but  he  always  recovered  the  true  path. 
It  is  in  these  moments  when  he  walked  hand  in  hand 
with  truth  that  we  must  lay  hold  of  him:  they  are  the 
landmarks  of  his  route  and  of  his  career. 

The  theoretical  idea  which  I  have  just  pointed  out 
prevented  him  from  believing  that  the  inactive  malic 
acid  was  a  paratartaric  acid.  Consequently,  it  must 
present  a  new  atomic  grouping  in  which  the  optical 
inactivity  results  not  from  a  compensation  between 
equal  and  opposed  forces  but  from  the  disappearance 
of  all  dissymmetry  in  the  active  molecule.  It  was  very 
audacious  to  imagine  a  new  theoretical  grouping  when 
there  were  already  three,  but  Pasteur  had  audacity  and 
this  audacity  had  often  served  him  well.  The  malic 
acid  which  he  studied  was  not,  we  have  said,  the  com- 
pound with  the  symmetrical  structure,  which  he  had 
dreamed  it  to  be.  Nevertheless  he  was  not  absolutely 
deceived,  for  this  body  with  a  symmetrical  structure 
exists  in  the  tartaric  series,  as  Pasteur  himself  was  to 
discover  a  little  later. 

Here  is  another  point  where  error  did  not  prevent  him 
from  arriving  at  the  truth.  Confident  in  his  idea  that 
he  had  an  aspartic  acid  and  a  malic  acid  with  a  sym- 
metrical molecule  not  contorted,  so  to  speak,  he  made  a 
careful  comparison  of  these  acids  with  the  twisted  and 
dissymmetrical  molecules  obtained  from  asparagin  and 
the  fruit  of  the  sorb-tree.  He  wished  to  see  how  this 
symmetry  or  dissymmetry  of  the  molecule  expressed 
itself  externally,  in  the  physical  and  chemical  characters 
of  the  acids  and  their  salts. 

From  this  study  he  derived  no  definite  knowledge  for 
two  reasons.     The  first  is  that  the  substances  to  which  he 


SUBSTANCES  INACTIVE  THROUGH  LOSS  OF  DISSYMMETRY  35 

turned  his  attention  were  not  fitted  to  answer  the  ques- 
tion asked.  But  of  that  Pasteur  was  unconscious. 
The  second  reason,  which  touched  him  closely,  is  that 
they  were  contradictory  in  their  responses.  The  active 
and  inactive  aspartates  resemble  each  other  very  much 
chemically  and  sometimes  differ  entirely  from  the  point 
of  view  of  crystallography,  even  to  the  degree  of  present- 
ing absolutely  incompatible  forms,  while  the  active  and 
inactive  malates,  very  similar  also  as  to  their  chemical 
composition,  are  sometimes  indistinguishable  in  a 
crystalline  state.  The  active  and  inactive  bimalates  of 
ammonia,  for  example,  have  the  same  crystalline  form 
and  the  same  angles.  One  is  often  in  danger  even  of 
taking  one  for  the  other,  for  it  happens  that  the  active 
bimalate  does  not  have  hemihedral  facets  and  corre- 
sponds exactly  in  form  with  the  inactive  bimalate. 

In  other  words,  all  the  order  and  harmony  observed  in 
the  tartrates  disappeared,  so  that  not  only  was  Pasteur 
obliged  to  abandon  without  an  answer  the  question  which 
he  had  put  to  himself  but  he  might  have  asked  himself 
anxiously  whether  in  the  tartrates  he  had  not  accident- 
ally fallen  upon  an  exceptional  case,  devoid  of  all  general 
bearing.  But  no!  Not  once,  it  seems,  did  this  doubt 
cross  his  mind.  At  least  his  writings  show  no  trace  of  it. 
From  the  contradictions  which  he  had  observed  he  con- 
cludes with  a  tranquil  assurance  that  the  crystalline 
form  has  only  a  secondary  importance,  since  in  the 
aspartates  and  the  malates  it  no  longer  shows  the  beauti- 
ful accord  with  the  optical  properties  which  are  so 
striking  in  the  tartrates.  He,  therefore,  deliberately 
threw  overboard  the  correlation  of  the  crystalline  form 
with  the  rotary  power,  which  remains  the  most  certain 
and  most  constant  evidence  of  molecular  dissymmetry. 

Let  us  pause  an  instant  to  observe  the  successive  steps 
which  we  have  made.     Herschel  gives  us  the  first  idea 


36  pasteur:  the  history  of  a  mind 

of  a  relation,  not  only  between  the  existence  of  a  rotary 
power  and  a  dissymmetry  of  construction  in  the  quartz 
crystal,  but  also  between  the  direction  of  this  power  and 
that  of  this  dissymmetry.  Biot  shows  us  subsequently 
that  the  rotary  power  can  exist  in  the  molecule.  Where- 
from  Pasteur  concludes  that  there  must  be  a  dissymmetry 
in  the  construction  of  the  molecule,  that  is  to  say  in  the 
arrangement  of  the  atoms.  He  finds  the  external  indica- 
tion of  this  dissymmetry  in  the  tartrates,  which  serve  him, 
furthermore,  to  state  precisely  the  meaning  of  this  word 
dissymmetry,  up  to  that  time  a  little  vague.  In  his 
mind,  then,  after  his  studies  on  the  aspartates  and 
malates,  these  tartrates  become,  as  did  the  quartz, 
merely  empty  shells,  after  yielding  the  idea  which 
they  contained.  This  idea  is  that  of  the  dissymmetry  of 
the  molecular  structure  and  of  its  constant  relation  to 
the  rotary  power. 

There  we  have  the  portion  of  truth  which  this  memoir 
contains!  On  reflection  the  conclusion  to  which  we 
arrive  will  appear  curious  from  the  philosophical  point  of 
view,  for  here  we  have  a  work  which  had  begun  by  estab- 
lishing a  close  relation  between  the  rotary  power  and  the 
crystalline  form,  and  which  ends  by  scorning  this  crystal- 
line form.  One  might  think  that  science  had  turned 
about  in  its  place  without  advancing.  But  he  would  be 
deceived,  for  here  we  see  clearly  how  much  a  matter  of 
indifference  it  is  whether  a  theory  or  a  doctrine  is  right, 
provided  that  it  incites  to  work,  and  results  in  the  dis- 
covery of  new  facts.  We  do  not  know  exactly  what  is 
the  relation  between  the  molecular  structure  and  the 
crystalline  form,  nor  even  if  there  is  a  relation  which 
makes  it  necessary  that  they  should  be  subject  one  to 
the  other.  Fundamentally  a  correlation  between  the 
existence  of  certain  crystalline  facets  and  the  arrange- 
ments of  atoms  in  the  molecule,  appears  to  us  rather 


SUBSTANCES  INACTIVE  THROUGH  LOSS  OF  DISSYMMETRY  37 

remote,  and  therefore  as  a  contingent,  but  the  fact  that 
the  idea  of  this  correlation  has  given  us,  through  Pas- 
teur, the  idea  of  the  dissymmetrical  structure  of  the 
molecule,  suffices  to  make  it  beneficial,  whether  false  or 
true. 

Here  we  have,  in  reality,  the  idea  which  has  come  forth 
from  it  quite  naturally,  like  the  grain  from  the  ear:  a 
molecule  which  possesses  the  rotary  power  is  dissym- 
metrical. But  a  dissymmetrical  molecule  cannot  be 
contained  in  one  plane  because  this  plane  would  be  for 
it  a  plane  of  symmetry.  Therefore,  the  molecule  must 
form  in  space  a  geometrical  solid  of  three  dimensions. 
That  is  the  first  conclusion.  Here  is  another:  as  we  are 
familiar  with  the  number  and  nature  of  atoms  entering 
into  the  molecule  we  may  attempt  to  arrange  them  in 
such  a  way  that  the  dissymmetry  of  the  solid  which  they 
form  corresponds  to  the  direction  of  the  rotary  power  of 
the  molecule.  Summed  up,  such  is  the  series  of  deduc- 
tions drawn  nearly  simultaneously  in  France  by  Le  Bel, 
in  Holland  by  Van-t-Hoff,  and  which  have  served  to 
found  a  new  science,  stereo-chemistry,  of  which  Pasteur 
is  thus  the  forerunner. 

Let  us  forget,  then,  all  the  false  interpretations  of  this 
memoir  on  aspartic  acid,  and  note  only  the  certainty 
with  which  Pasteur,  arrested  by  a  conception,  inexact  in 
the  case  to  which  he  applied  it,  but  the  general  justness 
of  which  the  future  was  to  confirm,  succeeded  in  tracing 
a  fourth  plan  of  construction  for  an  active  molecule. 
"We  are  here,"  he  would  have  been  able  to  say  at  this 
moment,  "thanks  to  the  discovery  of  inactive  substances, 
in  possession  of  a  fertile  idea.  A  substance  is  dissym- 
metrical, right  or  left:  by  certain  artifices  of  isomeric 
transformations,  which  must  be  sought  and  discovered  for 
each  particular  case,  it  can  lose  its  molecular  dissym- 
metry, be  twisted,  to  use  a  rough  comparison,  and  effect 


38  pasteur:  the  history  of  a  mind 

in  the  grouping  of  its  atoms  an  arrangement  with  a  super- 
posable  image.  Thus  each  dissymmetrical  substance 
offers  four  variations  or,  rather,  four  distinct  sub-species  : 
the  right-handed  body,  the  left-handed  body,  the  com- 
bination of  the  right  and  the  left,  and  the  body  which  is 
neither  right  nor  left,  nor  formed  by  a  combination  of  the 
two."1 

I  shall  dwell  no  longer  on  the  aspartic  and  malic  acids 
because,  as  I  have  just  said,  Pasteur  had  taken  the  wrong 
route.  This  has  been  evident  since,  and  it  is  singular 
that  its  discovery  has  required  no  new  methods;  it  has 
only  been  necessary  to  employ  those  methods  with  which 
he  has  made  us  familiar.  By  following  them  M.  Bremer 
has  shown  that  the  inactive  malic  acid  of  Pasteur  was  in 
reality  a  paratartaric  acid,  that  is  to  say,  a  combination 
of  right-  and  left-handed  acids.  It  has  been  discovered 
also  that  there  are  three  asparagins,  three  aspartic  acids, 
three  malic  acids,  and  that  the  maleic  acid  and  fumaric 
acid  are  more  distinct  than  Pasteur  believed  them,  and 
possess  a  new  dissymmetry  which  is  not  expressed  by 
the  appearance  of  a  rotary  power.  In  short,  our  knowl- 
edge has  been  very  much  extended  since  Pasteur  did  his 
work,  but  there  has  been  no  change  in  its  source,  and  in 
its  immense  development  it  remains  faithful  to  this  parent 
idea  of  Pasteur,  that  all  difference  in  the  grouping  of  the 
atoms  of  a  molecule  must  be  expressed  externally  in  some 
way.  That  Pasteur  was  sometimes  self-deceived,  and 
that  there  are  some  defective  stones  in  the  foundation 
which  he  has  given  to  the  edifice,  is  of  no  importance. 
The  essential  thing  is  that  the  edifice  rises  without 
crumbling,  and  that  it  does  rise. 

1  De  la  dissymétrie  moléculaire  des   produits    organiques  naturels. 
Leçon  professée  devant  la  Société  chimique.     1860. 


COMBINATIONS  BETWEEN   ACTIVE   MOLECULES  39 

IX 
COMBINATIONS  BETWEEN  ACTIVE  MOLECULES 

If  the  ideas  which  we  have  just  developed  have  served 
as  a  foundation  for  stereo-chemistry,  others  in  the  same 
group  will  lead  us  to  the  study  of  fermentations,  that  is 
to  say,  to  one  of  the  most  beautiful  conquests  of  this  cen- 
tury of  marvels.  For  this,  let  us  go  back  to  the  study 
of  the  tartrates.  We  have  seen  that  any  left-handed 
tartrate  is  the  twin  brother  of  the  corresponding  right- 
handed  one.  Save  that  they  bear  their  hemihedral  facets 
in  different  ways,  when  they  have  them,  and  that  they 
have  equal  rotary  powers  but  in  opposite  directions,  the 
two  brothers  are  exactly  alike  not  only  in  respect  to  their 
geometrical  form,  solubility,  density,  etc.,  but  also  in 
what  one  might  call  the  physiognomy  of  the  crystals. 
These  twin  crystals  are  equally  limpid  or  clouded,  hard 
or  fragile,  polished  or  striated;  they  have  the  same 
internal  fissures,  in  short,  they  cannot  be  distinguished 
unless  one  subjects  them  to  a  very  careful  examination. 
We  have  taken  exact  note  of  these  resemblances  in  order 
to  convince  ourselves  that  the  molecules  of  these  crystals 
are  identical  in  everything  save  their  atomic  arrange- 
ment. The  moment  has  come  to  consider  this  resem- 
blance from  another  point  of  view. 

Up  to  this  time  it  has  been  manifest  to  us  only  in  the 
combinations  of  the  right  and  left  tartaric  acids,  with 
certain  mineral  substances:  potash,  soda,  ammonia. 
Inactive  on  polarized  light,  as  the  minerals  are,  these 
substances  are  content,  so  to  speak,  with  diluting  the 
active  power  of  the  tartaric  acid  on  entering  into  combi- 
nation with  it.  But  what  happens  if  one  combines  these 
tartaric  acids  with  active  substances?  If  the  latter,  as 
is  probable,  maintain  their  power  in  the  compound,  this 


40  pasteur:  the  history  of  a  mind 

power  will  be  contrary  to  that  of  one  of  the  tartrates, 
and  will  exalt  that  of  the  other.  What  will  be  the  out- 
come of  this  internal  conflict  on  the  physical  and  chem- 
ical properties  of  the  compound?  It  does  not  seem, 
a  priori,  that  it  will  be  expressed  externally  in  the  same 
way  as  the  harmonious  dissymmetry  of  the  tartrates. 
What  does  experiment  say? 

Impelled  by  this  ingenious  and  original  idea,  which, 
let  us  remark,  was,  moreover,  from  the  point  of  view 
of  the  history  of  his  mind,  a  logical  consequence  of  his 
conceptions,  Pasteur  tried,  in  fact,  to  combine  with 
active  malic  acid  and  its  compounds,  the  right-  and  left- 
handed  tartaric  acids  and  their  compounds,  asparagin 
with  the  two  tartaric  acids,  etc.  Between  the  different 
substances  thus  produced  he  actually  determined  some 
differences  greater  than  those  existing  between  the 
corresponding  substances  formed  by  means  of  inactive 
bodies.  But  the  results  are  clearer  when  one  combines 
the  tartaric  acids  with  the  organic  alkalies  of  plants, 
quinine,  cinchonine,  brucine,  strychnine,  etc.,  endowed 
also  with  the  rotary  power.  The  identity  of  the  chem- 
ical properties  which  existed  in  the  tartrates  with 
mineral  bases  disappears.  The  right- and  left-handed 
tartrates  of  the  organic  alkalies  are  no  longer  either  equally 
soluble  or  equally  hydrated.  They  bear  very  unequally 
the  action  of  heat,  and  they  lose  more  or  less  easily  then- 
water  of  crystallization.  If  by  chance  their  chemical 
formula  is  the  same  their  crystalline  forms  are  different 
and  incompatible.  Finally,  sometimes,  with  aspara- 
gin, for  example,  combination  is  possible  with  the  right- 
handed  body,  impossible  with  the  left.  As  for  their 
rotary  powers,  instead  of  being  equal  and  opposite,  as  in 
the  case  of  the  combinations  of  the  tartaric  acids  with 
mineral  bases,  there  may  be  either  addition  or  subtrac- 
tion, and  the  resultant  deviation  is  very  different  in  the 


COMBINATIONS   BETWEEN    ACTIVE    MOLECULES  41 

right-  and  left-handed  tartrates  in  combination  even  with 
the  same  organic  alkali.  In  short,  we  observe  some 
differences  which  can  be  attributed  legitimately  only  to 
the  reciprocal  influences  of  the  acid  and  the  base  in 
combination. 

And,  thenceforth,  we  are  authorized  to  philosophize 
with  Pasteur.  It  is  very  probable  that  all  natural, 
active  bodies  present,  like  tartaric  acid,  at  least  three 
forms,  the  right,  the  left,  and  the  para.  Then  when  we 
combine  two  substances  each  of  which  has  its  right,  left 
and  inactive  form,  it  is  possible  to  obtain  nine  different 
combinations,  identical  as  far  as  the  number  and  nature 
of  the  atoms  is  concerned,  but  different  in  their  arrange- 
ments. This  difference  of  arrangement  will  admit 
of  the  addition  of  an  unequal  number  of  molecules 
of  water  of  crystallization  which  will  be  more  or  less 
difficult  to  drive  away  with  heat.  It  will  involve, 
furthermore,  differences  in  crystalline  form,  in  solu- 
bility, and  in  chemical  stability.  On  the  whole,  it  is 
sufficient  to  constitute  nine  different  substances,  which 
number  could  be  increased  to  sixteen  if  we  take  into 
consideration,  in  addition  to  the  three  forms  pointed 
out  above,  the  form  by  nature  inactive,  which  Pasteur 
had  not  yet  discovered  in  the  tartaric  acid. 

Of  a  complete  series  there  was  no  example  at  the  time 
when  Pasteur  worked,  and  I  do  not  know  whether  there 
is  one  to-day.  Then,  there  were  only  some  scattered 
terms  but  these  permitted  the  beginning  of  proof. 
Precisely  the  combination  of  the  right-handed  tartaric 
acid  with  the  left  appears  in  the  forecasts  above  made, 
and  it  is  remarkable  that  one  finds  between  the  tartrates 
and  paratartrates  differences  of  the  same  order  as  those 
which  we  have  just  pointed  out.  The  chemical  com- 
position is  ordinarily  not  the  same,  the  crystalline  forms 
are   incompatible,    the    solubilities    are    different,    etc. 


42  pasteur:  the  history  op  a  mind 

It  is  true  that  this  is  not  always  the  case,  and  Pasteur 
would  have  been  able  to  find  contrary  examples  in  the 
history  of  the  malates  if  he  had  not  made  the  error  which 
we  have  pointed  out  above.  But,  on  the  whole,  one 
can  accept  this  way  of  looking  at  it  as  sufficiently  ex- 
act, and  Pasteur  was  right  to  introduce  it  into  science. 
The  marked  differences  which  one  observes  between  the 
various  sugars  encountered  in  nature,  for  example  be- 
tween rock  candy  and  its  constituent  sugars,  are  evidently 
of  the  same  order  and  have  the  same  origin.  I  will  ven- 
ture to  add  that  it  is  reasons  of  the  same  kind  which  render 
so  baffling  the  study  of  albuminoid  substances,  in  which 
differences  of  molecular  structure  are  expressed  exter- 
nally otherwise  than  by  differences  in  crystallization. 

If  we  now  recall  that  the  protoplasm  of  all  living 
cells  is  endowed  with  the  rotary  power,  that  it  con- 
tains, therefore,  dissymmetrical  molecules,  and  that 
this  dissymmetry  in  relation  to  the  stability  or  insta- 
bility of  the  compound,  cannot  fail  to  play  a  rôle  in  all 
the  chemical  combinations  of  which  the  protoplasm  is 
the  seat,  we  shall  conclude  that  there  are  in  these  con- 
siderations indications  of  a  profound  mechanism  of  life. 
We  encounter  here  one  of  those  flights  of  imagination 
which  Pasteur  permitted  himself  sometimes  and  which 
were  for  him  the  recompense  and  the  repose  derived 
from  works  of  research.  But  when  he  had  thus  boldly 
explored  the  horizon  he  made  haste  to  regain  the  solid 
ground  of  experiment.  Let  us  follow  his  example  and 
enter  the  laboratory. 


MEANS   OF   SEPARATING   ROTARY   SUBSTANCES  43 

X 

MEANS  OF  SEPARATING  THE  RIGHT- AND  LEFT- 
HANDED  SUBSTANCES 

We  have  to  deduce  from  the  preceding  facts  one  of  the 
consequences  which  they  allow.  Now  that  we  have 
substances  of  the  same  composition  into  the  molecule 
of  which  we  can  introduce  either  an  identity,  or  foreseen 
and  premeditated  variations,  let  us  ask  ourselves  if  we 
cannot  impart  to  the  two  tartrates,  right  and  left,  which 
precipitate  at  the  same  time  from  a  solution  of  the  double 
paratartrate  of  soda  and  ammonia,  a  difference  in  solu- 
bility great  enough  so  that  one  will  be  deposited  before 
the  other,  when  the  liquid  is  left  to  evaporate.  That 
would  be  a  great  advantage.  At  present,  we  only  know 
how  to  separate  them  by  hand,  observing  individually 
their  hemihedral  facets  in  order  to  determine  how  they 
are  placed  on  the  crystal.  That  demands  time,  patience, 
and  a  profound  knowledge  of  crystalline  forms.  Further- 
more, when  deposited,  the  crystals  are  generally  in  a 
mass,  and  one  is  never  sure  that  a  right-handed  crystal 
which  one  detaches  from  the  mass  does  not  bear  with 
it  fragments  of  a  left-handed  one.  The  separate  crystal- 
lization of  the  two  salts  would  certainly  yield  them  in  a 
much  purer  state. 

Let  us  search  then  in  this  direction,  Pasteur  surely 
said,  and  he  soon  found,  in  reality,  that  in  crystallizing 
the  paratartrate  of  cinchonine,  the  left-handed  tartrate 
which  is  less  soluble  was  deposited  first,  and  to  such  an 
extent  that  by  decanting  at  a  given  moment  the  mother 
liquid,  and  evaporating  it  anew,  there  was  found  in  it 
only  the  right-handed  tartrate.  It  was  a  natural  separa- 
tion of  the  two  acids,  otherwise  so  similar.  I  imagine 
that  when  Pasteur  performed  this  experiment  for  the 


44  pasteur:  the  history  of  a  mind 

first  time  he  was  no  less  happy  than  when  he  saw  the 
double  paratartrate  of  soda  and  ammonia  break  up 
unexpectedly.  That  was  an  unforeseen  discovery  on  his 
pathway;  here,  on  the  other  hand,  the  discovery  was 
searched  for  and  foreseen,  which  doubled  the  interest  of 
it.  The  paratartrate  of  cinchonine  is  not,  moreover, 
the  only  one  which  lends  itself  to  such  a  separation: 
that  of  quinicine  is  similar,  but  in  this  case  it  is  the  right- 
handed  tartrate  which  is  deposited  first. 

We  are,  then,  in  possession  of  a  second  means  of 
separating  the  active  components  of  a  paratartaric  acid. 
Let  us  say  immediately  that  it  is  by  this  method  that 
M.  Bremer  demonstrated  the  inactive  malic  acid  of 
Pasteur  to  be  in  reality  a  combination  of  the  right-  and 
the  left-handed  acids.  Let  us  say,  also,  that  a  third 
means  was  conceived  by  M.  Gernez  in  the  laboratory 
of  Pasteur.  It  was  incident  to  the  preceding  in  that  the 
separate  crystallization  of  the  two  tartrates  was  provoked, 
not  by  differences  in  solubility,  but  by  a  suitable  crystal- 
line decoy  introduced  into  the  supersaturated  solution. 
With  a  decoy  formed  of  right-handed  tartrate  one  ob- 
tained the  crystallization  of  the  right-handed  tartrate; 
with  one  of  the  left-handed  tartrate,  that  of  the  left 
tartrate.  This  was,  then,  under  another  form,  it  is  true, 
a  dissymmetrical  influence  introduced  to  obtain  the 
separation. 

Another  means  discovered  by  Pasteur  is  still  more 
curious  and  introduces  us  into  the  realm  of  life.  It  had 
been  known  for  a  long  time  that  lime  tartrate  left  to 
itself  under  water  decomposes  with  the  formation  of 
various  products.  One  day  Pasteur  observed  a  solution 
of  right  tartrate  of  ammonia  placed  in  a  flask  in  the 
laboratory  to  be  decomposing  in  the  same  way.  The 
liquid  which  was  at  first  clear  (let  us  keep  this  fact  in 
mind  because  we  shall  need  it  later)  became  clouded 


MEANS   OF   SEPARATING   ROTARY   SUBSTANCES  45 

as  the  result  of  the  development  of  one  of  those  organisms 
which  invade  infusions,  and  then  a  drop  of  this  clouded 
liquid  sufficed  to  induce  a  fermentation  in  a  new  flask. 

Thus  far  nothing  surprising:  we  have  before  our  eyes 
one  of  those  phenomena  of  decomposition  of  organic 
matter  which  are  constantly  taking  place  around  us. 
But  here  is  where  the  investigator  awakes  and  the  origin- 
ality begins.  For  others  the  fact  was  commonplace;  for 
Pasteur  it  was  life  engaged  in  a  struggle  with  a  compound 
endowed  with  rotary  power.  This  form  of  plant  life 
which  grew  and  developed  in  the  flask  was  composed  of 
cells  giving  birth  to  dissymmetrical  products,  as  do  all 
living  cells,  and  then  there  presented  itself  quite  natur- 
ally and  imperatively  the  following  question  :  how  will 
this  organism  behave  in  a  solution  of  paratartrate? 

Let  us  transfer  a  drop  of  the  fermented  liquid  of  right 
tartrate  of  ammonia  to  a  solution  of  paratartrate  of 
ammonia.  Things  follow  their  course,  and  nothing  out- 
wardly distinguishes  these  two  fermentations.  But  let 
us  study  them  with  a  polarization  apparatus.  Let  us 
filter,  at  definite  intervals,  a  portion  of  the  solution  of 
paratartrate  and  pass  through  it  a  ray  of  polarized 
fight,  and  we  shall  see  that  this  liquid,  inactive  in  the 
beginning,  has  acquired  a  left  rotary  power  which  in- 
creases little  by  little  till  it  reaches  a  maximum.  At 
this  moment  fermentation  is  suspended,  the  liquid  clears, 
it  contains  no  longer  any  of  the  right-handed  salt  which 
is  the  only  one  the  fermentation  has  attacked  and  trans- 
formed. The  left-handed  salt  has  been  respected  and 
can  be  recovered  by  evaporation. 

The  phenomena,  it  is  true,  do  not  always  proceed 
in  just  this  manner.  Everything  depends  on  the  micro- 
scopic organism  which  is  sown,  and  developed,  in  the 
liquid.  Pasteur  has  never  described  the  one  which  he 
observed;  it  would  seem  that  he  had  been  working  with  a 


46  pasteur:  the  history  or  a  mind 

species  of  Pénicillium.  Since  then  Pfeffer  has  found  a 
bacterium  which  acts  like  the  species  studied  by  Pasteur. 
On  the  contrary,  a  bacterium  that  developed  spontane- 
ously in  the  laboratory,  in  a  solution  of  left-handed  tar- 
trate of  soda  and  ammonia,  consumes  by  preference 
the  left  tartrate  from  a  solution  of  paratartrate,  although 
it  is  quite  able  to  attack  the  right  also.  Other  living 
species  consume  indifferently  the  two  salts,  and  all 
cases  are  possible.  But  we  are  none  the  less  in  possession 
of  this  fact:  that  the  nutritive  character  of  a  tartrate 
may  bear  a  relation  to  its  molecular  dissymmetry. 


XI 
GENERAL  CONCLUSIONS 

This  fact  merits  special  attention.  The  right-  and 
left-handed  tartrates  of  ammonia  are  composed  of  ex- 
actly the  same  elements,  carbon,  hydrogen,  oxygen, 
nitrogen,  in  the  same  quantity.  The  only  difference  is  in 
the  arrangements  of  the  atoms.  Still  this  difference  is 
not  great  since  the  two  arrangements  are  the  image  of 
each  other  in  the  mirror,  and  nevertheless  it  is  great 
enough  so  that  a  living  organism  can  respect  one  of  the 
two  salts  while  it  entirely  destroys  the  other. 

To  understand  this  fact  it  is  evidently  necessary  to 
relate  it  to  what  we  know  on  the  subject  of  the  difference 
in  chemical  properties  brought  about  by  combination 
of  tartaric  acid  with  an  active  substance.  In  the  pres- 
ence of  potash  and  soda  the  right  and  left  tartaric 
acids  behave  exactly  alike  and  have  the  same  stability. 
This  is  no  longer  the  case  when  they  unite  with  sub- 
stances having  rotary  power.  Now  it  is  just  these  which 
they  encounter  in  the  living  tissues  where  there  are 


PASTEUR 

(From  an  engraving  by  Noyés.) 
(Courtesy  of  the  Library  of  the  Surgeon  General.) 


GENERAL   CONCLUSIONS  47 

always  active  substances  though  it  may  be  only  the 
albuminoid  matter  of  the  protoplasm. 

On  the  other  hand,  all  phenomena  of  nutrition  are 
protoplasmic,  that  is  to  say  the  food  of  any  cell,  whatever 
that  food  and  whatever  the  cell,  must  begin  by  forming 
a  part  of  the  protoplasm  before  being  consumed  or 
utilized.  From  this  we  understand  that  the  two  tar- 
trates do  not  lend  themselves  with  the  same  facility 
to  this  combination,  or,  that  once  combined,  they  have 
different  stabilities.  Thus  it  is  that  the  active  bimalate 
unites  with  the  right-handed  bitartrate  to  give  a  crystal- 
line combination  unrealizable  with  the  left-handed 
bitartrate.  Thus  it  is  that  the  two  tartrates  of  quinine 
are  quite  dissimilarly  resistant  to  the  action  of  heat. 

A  living  cell  appears  to  us,  therefore,  as  a  laboratory 
of  dissymmetrical  forces,  where  a  dissymmetrical  pro- 
toplasm acting  under  the  influence  of  the  sun,  that  is  to 
say,  under  the  influence  of  dissymmetrical  exterior  forces, 
may  preside  over  quite  varied  actions,  may  manufacture 
in  its  turn  new  dissymmetrical  substances  which  add 
to  or  take  away  from  its  power,  may  utilize  one  of  the 
elements  of  a  paratartaric  acid  without  touching  the 
other,  may  manufacture  crystallizable  sugar  at  one 
moment  to  consume  it  at  another,  make  reserve  foods 
today  and  exhaust  them  tomorrow,  in  brief,  may  show 
the  marvelous  plasticity  which  we  know  to  be  char- 
acteristic of  it,  and  all  that  very  simply,  without  any 
stir,  by  means  of  very  small  deviations  of  forces  under 
dissymmetrical  influences. 

The  nature  of  the  albuminoid  substance  of  each  cell,  or, 
to  speak  more  generally,  the  direction  of  the  dissym- 
metry of  one  or  several  of  the  elements  of  its  protoplasm, 
exerts  thu  ^n  its  functions  and  therefore  on  its  develop- 
ment, an  influence  of  the  first  order,  the  mechanism 
of  which,  obscure  up  to  this  time,  is  a  little  clearer  when 


48  pasteur:  the  history  of  a  mind 

seen  in  the  light  of  Pasteur's  work.  What  kind  of  a 
world  would  it  be  in  which  one  would  replace  the  cellu- 
lose and  albumen  in  the  actually  living  cells  by  their 
opposites  and,  to  recall  to  our  minds  that  which  we 
have  already  gone  over,  what  kind  of  a  world  would  it  be  in 
which  the  earth  should  turn  around  the  sun  in  a  direction 
opposite  to  that  which  it  now  takes,  an  earth  where  the 
electric  current  which  makes  of  it  a  magnet  should  take 
an  opposite  direction  and  where  the  point  of  the  compass 
needle  which  marks  the  north  should  mark  the  south? 

We  are  right  in  thinking  that  it  would  be  a  world  not 
identical  with  the  actual  world.  We  may  even  believe 
that  it  would  differ  very  much,  and  behold  therein  the 
profound  thought  of  Pasteur,  the  bond  which  unites 
our  nature  to  cosmic  phenomena.  We  are  all  the 
children  of  the  sun,  as  someone  has  said,  speaking  from 
another  viewpoint.  We  see  here  more  than  that.  The 
sun  not  only  distributes  the  force,  but  it  influences  its 
direction  and  its  use. 

We  see  also,  at  the  same  time,  all  the  difficulty  which 
one  would  encounter  in  approaching  the  problem  by 
experiment.  In  order  to  introduce  into  a  cell  proxi- 
mate principles  different  and  opposite  from  those  which 
exist  there,  it  would  be  necessary  to  act  upon  it  at  the 
time  of  its  greatest  plasticity,  that  is,  to  take  the  germ 
cell  and  try  to  modify  it.  But  this  cell  has  received 
from  its  parents  a  heredity  in  the  form  of  one  or  several 
active  substances,  the  presence  of  which  is  sufficient 
to  render  it  rebellious  to  certain  actions  and  to  make  it 
accept  others,  that  is  to  say,  to  impart  to  its  evolution 
a  definite  direction.  This  cell  contains  in  the  beginning 
not  only  its  being  but  also  its  becoming,  and  it  is  therefore 
an  initial  force  which  augments  without  ceasing  by  giving 
its  own  direction  to  new  forces  which  appear  every 
day  in  the  little  world  it  governs.     Vires  acquirit  eundo. 


GENERAL   CONCLUSIONS  49 

And  the  life  of  the  whole  results  from  the  sum  total  of 
these  cellular  lives. 

Ah!  If  spontaneous  generation  were  possible!  If 
one  could  create  a  living  whole,  could  cause  to  evolve 
from  inactive  mineral  matter  a  living  cell,  how  much 
easier  it  would  be  to  give  it  a  direction,  to  make  these 
foreseen  dissymmetries  of  which  we  have  spoken 
enter  into  its  substance  and  thence  into  its  vital  mani- 
festations! I  am  adding  something  to  what  Pasteur 
has  written  on  these  captivating  questions,  but  I  do  not 
believe  that  I  have  gone  beyond  what  was  in  his  thought 
in  my  effort  to  show  how  the  methodical  and  regular 
study  of  the  questions  which  ranged  themselves  before 
him,  as  he  advanced,  was  able  to  put  him  in  the  presence 
of  two  of  the  problems  which  it  was  fated  that  he  should 
solve:  the  question  of  fermentations  and  that  of  spon- 
taneous generations. 


PASTEUR 

(From  an  old  Lithograph.) 

(Courtesy  of  Capt.  J.  C.  Pryor,  Naval  Med.  School,  Washington 

D.  C.) 


SECOND  PART 
Lactic  and  Alcoholic  Fermentations 


THE  KNOWLEDGE   OF  FERMENTATIONS  BEFORE 
LAVOISIER 

At  the  time  Pasteur  approached  it,  the  question  of 
fermentations  formed  such  a  confused  mass  that  not  only 
is  it  difficult  to  picture  to  ourselves  what  the  chemists 
of  the  epoch  thought  of  it  but  we  doubt  even  whether 
they  had  any  clear  idea  of  it,  we  find  so  many  con- 
tradictions and  singular  statements  in  their  writings. 
When  we  seek  to  discover  whence  came  that  embryonic 
notion  respecting  fermentation,  persistent  to  the  middle 
of  the  nineteenth  century,  we  see  that  it  was  due  not  to 
the  difficulties  of  the  subject,  but  to  the  fact  that  the 
question  had  been  a  philosophical  one  before  it  became 
a  scientific  one. 

The  phenomena  of  fermentation  are  as  old  as  the 
world,  and  the  first  that  man  learned  to  control  and  to 
adapt  to  his  needs  are  probably  those  which  lead  to  the 
production  of  bread  and  wine.  More  time  and  effort 
doubtless  was  required  to  procure  beer.  Once  found, 
it  was  inevitable  that  the  methods  which  yielded  these 
articles  of  food  and  drink  should  spread  rapidly  and 
soon  become  common.  The  bubbling  which  takes 
place  spontaneously  in  the  mass  of  vintage,  or  which  is 
produced  in  the  barley  wort  by  the  addition  of  the  yeast 
of  beer,  the  change  of  savor  and  texture  which  result 
from  the  introduction  of  yeast  into  the  flour  paste  are 

51 


52  pasteur:  the  history  of  a  mind 

phenomena  too  curious  not  to  have  attracted,  from 
the  beginning,  the  attention  of  philosophers,  who  con- 
tented themselves  with  borrowing  from  them  comparisons 
and  figures,  and  the  curiosity  of  searchers  for  the  philos- 
opher's stone,  who  were  less  disinterested.  Might 
not  a  base  metal  be  transformed  into  a  precious  one 
by  means  analogous  to  that  which  derived  a  savory 
bread  from  an  indigestible  paste?  Is  there  not  some 
powder  of  transmutation  acting  like  a  ferment?  Here 
we  have  the  question  which  the  alchemists  asked 
themselves  and  which  naturally  they  did  not  solve, 
first  because  it  is  insoluble,  second  because  though  they 
were  experimenters,  they  were  still  more  logicians, 
believing  in  the  power  of  the  idea,  and  inclined  to  sub- 
ordinate experiment  to  it. 

It  is  not  that  there  do  not  exist  in  their  writings 
phrases  in  which,  if  one  is  so  inclined,  it  is  possible  to 
see,  like  the  break  of  day,  the  forecast  of  recent  discov- 
eries. But  in  reading  these  ancient  authors  we  must 
always  bear  in  mind  that  the  word  with  them  has  often 
preceded  the  idea  because  of  the  general  mode  of 
education  of  the  middle  ages,  and  that  in  the  sciences 
the  idea  has  almost  always  preceded  the  fact.  The 
word  has  no  value  of  its  own;  an  idea,  so  long  as  it 
remains  a  view  of  the  mind,  is  always  balanced  by  an 
opposing  idea;  the  fact  alone  is  convincing  and  brings 
certainty.  But  facts  are  what  the  alchemists  scarcely  ever 
found  on  the  question  of  fermentation.  The  defini- 
tions of  it  which  they  have  given  are  only  obscure  or 
pretentious  paraphrases  of  the  phenomena  observed  in  the 
manufacture  of  wine  or  of  bread.  They  make  allusions 
sometimes  to  the  setting  free  of  gas  (exaltatio),  sometimes 
to  the  fact  that  the  fermented  bread  can,  in  its  turn, 
act  as  a  yeast  (immutatio).  But  as  they  knew  nothing 
of  the  nature  of  the  substance  which  ferments,  nor  of 


FERMENTATIONS  BEFORE    LAVOISIER  53 

that  of  the  products  of  fermentation  (saye  that  of 
alcohol,  known  for  a  long  time),  it  is  difficult  for  them  to 
escape  glittering  generalities. 

The  honor  of  having  provoked  serious  studies  by 
showing  the  worthlessness  of  the  little  that  was  known 
belongs  to  Paracelsus  (1493-1541).  Although  of  new 
facts  he  himself  contributed  very  few,  his  militant  way, 
his  great  mind,  his  disdain  for  traditions  and  the  philo- 
sophical speculations  which  at  that  time  dominated 
science,  all  these  brilliant  and  substantial  qualities, 
could  not  fail  to  have  a  powerful  influence  on  his  con- 
temporaries. To  the  attraction  of  the  studies  in  them- 
selves he  added  the  allurement  of  a  close  personal  in- 
terest. To  him,  man  was  a  chemical  compound;  diseases 
were  caused  by  some  alteration  in  this  compound;  the 
putrid  fevers,  for  example,  were  due  to  excremental 
substances,  which  instead  of  being  rejected  were  retained 
in  the  economy.  Hence,  the  utility  of  searching  for 
chemicals  which  could  combat  efficaciously  these 
maladies.  Paracelsus,  we  see,  might  be  cited  as  the  fore- 
runner of  the  theory  of  antitoxins.  The  truth  is  that 
he  argued  well,  but  it  was,  after  all,  only  argument. 

This  association  between  the  phenomena  of  fermenta- 
tion and  disease  does  not  really  date  from  Paracelsus. 
It  influenced  his  predecessors:  it  furthermore  influenced 
his  successors  down  to  Pasteur,  who  gave  it  a  precise 
significance.  We  find  it  becoming  more  and  more  clearly 
defined  from  the  beginning  of  the  seventeenth  century, 
which  opens  the  era  of  work  and  discovery.  It  takes  an 
experimental  turn  with  Van  Helmont,  who  discovered 
carbonic  acid  in  respiration,  putrefaction,  digestion,  and 
in  the  fermentation  of  wine;  with  Bêcher,  who  passed 
several  years  in  the  practice  of  fermentations  and  whose 
writings  profited  by  his  long  experience.  Unfortunately 
dissertation  regained  ascendancy  with  R.  Boyle,  in  other 


54  pasteur:  the  history  of  a  mind 

respects  so  original,  and  especially  with  Stahl,  whose 
influence  on  his  century  was  so  great.  His  was  a  high 
intelligence,  a  powerful  and  generalizing  mind,  but  he 
believed  in  fencing  with  words,  and  was  not  a  scientific 
man. 

He  introduced  into  his  theory  of  fermentation,  sus- 
taining them  with  his  great  authority,  ideas  already 
professed  by  Willis.  According  to  Stahl,  "Every  sub- 
stance in  a  state  of  putrefaction  easily  transmits  this 
state  to  another  body  still  free  from  decay.  Thus  it  is 
that  a  similar  body  animated  already  by  an  internal 
movement  (let  us  bear  this  idea  in  mind  for  we  shall 
find  it  again  in  Liebig),  may,  with  the  greatest  facility, 
involve  in  the  same  internal  movement  another  body 
still  in  repose  but  disposed  by  nature  to  a  similar  move- 
ment. *  *  *  There  are  two  periods  in  fermentation  thus 
considered  as  the  result  of  an  internal  movement;  in 
the  first,  the  different  molecules  of  the  fermenting  sub- 
stances are  gently  agitated,  and  some  parts,  more  or  less 
attenuated,  gather  together;  in  the  second,  the  parts 
separate  themselves  from  the  mixture  as  a  result  of  the 
movement  which  animates  them,  and  the  analogous 
parts  reunite  to  the  exclusion  of  the  others." 

According  to  Stahl,  the  ferment  intervenes  only  to 
communicate  its  movement  to  the  analogous  parts  of 
the  liquor  to  be  fermented.  Its  action,  therefore,  we 
should  say  today,  is  purely  dynamic.  Let  us  hasten 
to  remind  ourselves  once  more  that  we  must  not  read 
into  the  phrases  of  the  ancients  our  modern  ideas.  The 
conception  of  Stahl  derives  its  fundamental  origin  from 
two  classes  of  facts,  the  manufacture  of  bread  and  of 
wine  :  the  first  a  transformation  arrested  at  its  beginning, 
during  which  the  agitation  is  feeble  and  in  which  the  parts 
in  the  vicinity  of  the  ferment  become  fermented  in  their 
turn;  the  second  characterized,  on  the  contrary,  by  a 


PEEMENTATIONS  BEFORE    LAVOISIER  55 

violent  movement,  which  communicates  to  the  liquid 
the  gas,  or  spirit,  which  is  set  free.  Adjust  these  two 
phenomena,  end  to  end,  generalize  them,  and  you  have 
the  definition,  cited  above,  of  Stahl  and  his  predecessors. 
If  with  Stahl  it  ended  in  assuming  a  more  definite  form, 
it  was  because  the  atomic  theories  of  Descartes  had 
penetrated  into  chemistry.  Save  for  this  addition  from 
without,  which  appeared  rather  in  the  way  of  stating 
it  than  in  the  idea  itself,  the  theory  of  Stahl  says  nothing 
more  than  that  of  Lefèvre  and  Lémery,  and  other 
chemists  of  the  time.  It  has  been  said  of  this  theory 
that  it  was  philosophical  and  seducing.  A  theory  does 
not  need  to  be  philosophical  and  seducing;  it  does  not 
even  need  to  be  true  in  the  absolute  sense  of  the  word, 
as  we  have  shown;  it  suffices  that  it  be  fertile.  But 
the  theory  of  Stahl  was  not  fertile. 

Progress  in  the  field  of  fermentation  came  from  without 
and  had  for  its  origin  new  facts  observed  in  the  study  of 
gas  by  scientific  men  who  were  contemporaries  of  Stahl. 
Moitrel  d'Elément  (1719)  learned  to  make  gases  visible 
by  passing  them  through  water;  Hales  (1677-1761) 
showed  how  to  manipulate  them;  Black  (1728-1799), 
how  to  distinguish  them  one  from  another.  He  isolated 
especially  carbonic  acid,  learned  to  know  its  properties, 
and  discovered,  something  which  Van  Helmont  had  not 
been  able  to  do,  that,  aside  from  alcohol,  it  is  the  sole 
product  of  the  transformation  of  sugar  in  the  alcoholic 
fermentation.  He  placed  thus  in  the  hands  of  the 
chemists  all  the  principal  elements  for  the  solution  of 
the  problem;  it  remained  only  to  coordinate  these  ele- 
ments and  to  establish  their  mutual  relations:  this  was 
the  work  of  Lavoisier. 


56  pasteur:  the  history  of  a  mind 

II 
FROM  LAVOISIER  TO  GAY-LUSSAC 

Here  we  are  able  to  point  out,  as  we  have  done  with 
respect  to  the  introduction  of  polarization  into  chemistry, 
the  fruitful  power  of  a  new  instrument  entering  into  a 
science  which  had  previously  not  known  it  or  had  ne- 
glected it.  It  is  to  the  introduction  of  the  balance 
into  chemistry  that  Lavoisier  owes  his  glory;  it  had  served 
him  well  in  the  solution  of  other  problems:  it  solved 
also  the  problem  of  fermentation.  Lavoisier  placed  on 
the  pan  of  a  balance  a  vessel  filled  with  water  to  which 
he  had  added  a  given  weight  of  sugar  and  a  little  yeast  of 
beer.  From  the  loss  of  weight  undergone  by  this  vessel 
at  the  end  of  the  fermentation,  he  inferred  the  weight 
of  the  carbonic  acid1  liberated  during  the  process  of  the 
phenomenon.  He  then  separated  the  alcohol  by  dis- 
tillation, weighed  it,  and  found  that  the  sum  of  the 
weights  of  the  alcohol  and  the  carbonic  acid  gave  very 
nearly  the  original  weight  of  the  sugar.  The  conclusion 
is  easy  to  draw  :  the  sugar  simply  breaks  up  into  alcohol 
and  carbonic  acid;  there  are  no  other  normal  products 
of  the  transformation. 

But  there  is  more  than  that  in  the  experiment  of 
Lavoisier.  The  relation  which  exists  between  the  weight 
of  the  sugar  on  the  one  hand  and  that  of  the  alcohol 
and  carbonic  acid  on  the  other,  ought  also  to  be  verified 
individually  for  each  one  of  the  elements  of  these  bodies. 
The  carbon  of  the  sugar  ought,  for  example,  to  be  found 
entire  in  that  of  the  alcohol  and  the  carbonic  acid;  the 
same  should  be  true  for  the  hydrogen  and  the  oxygen. 

1  Following  the  usage  of  Pasteur  and  his  opponents  and  all  the  older 
writers,  this  book,  which  is  an  interpretation,  calls  the  dissolved  gas  and 
the  free  gas,  indifferently,  carbonic  acid.     Trs. 


PASTEUR 

(At  Forty-five.) 


FROM   LAVOISIER   TO   GAY-LUSSAC  57 

It  is  sufficient,  therefore,  to  know  the  composition  of 
the  sugar,  of  the  alcohol  and  of  the  carbonic  acid,  in 
order  to  prepare  the  balance  sheet  of  the  reaction,  which 
Lavoisier  sums  up  in  these  clear  terms:  "The  results 
of  the  vinous  fermentation  are  reduced,  therefore,  to 
separating  into  two  portions  the  sugar  which  is  an  oxide, 
oxidizing  one  at  the  expense  of  the  other  to  form  car- 
bonic acid,  deoxidizing  the  other  at  the  expense  of  the 
first,  to  form  out  of  it  a  combustible  substance  which 
is  the  alcohol,  so  that,  if  it  were  possible  to  recombine 
these  two  substances,  the  alcohol  and  the  carbonic  acid, 
we  should  again  obtain  sugar." 

Here,  apparently,  we  have  reached  a  truly  scientific 
ground,  and  it  seems  as  though,  from  this  point  on, 
progress  will  be  made  in  great  strides.  But  this  problem 
is  unlike  others;  everything  in  its  course  has  been  un- 
certain and  laborious;  it  even  exhibits  this  fact,  not 
rare,  but  always  curious,  namely,  that  its  progress  has 
been  due  as  much  to  error  as  to  truth. 

The  conclusions  of  Lavoisier  were  exact  but  his  work 
was  not.  Because  of  the  lack  of  good  analytical  methods 
he  was  deceived  in  the  composition  of  the  sugar  employed, 
and  in  that  of  the  alcohol  produced.  And  if,  in  spite 
of  these  errors,  which  should  have  vitiated  everything, 
he  reached  a  conclusion  correct  in  its  general  features, 
it  was  due  entirely  to  a  chance  compensation  of  errors. 
Happy  chance,  one  might  say,  providential  chance,  which 
has  had  such  enduring  and  useful  consequences  ! 

Useful,  for  Lavoisier  had  apparently  so  clearly  ex- 
plained the  mystery  of  fermentation,  had  reduced  it  to  a 
formula  so  simple,  that  the  idea  of  this  simplicity  has 
never  left  the  minds  of  scientific  men.  This  became 
apparent  when  Gay-Lussac  and  Thénard,  after  having 
perfected  the  processes  of  organic  analysis,  determined 
the  exact  composition  of  cane-sugar.     It  was  then  very 


58  pasteur:  the  history  op  a  mind 

easy  to  be  convinced  that  all  Lavoisier's  conclusions 
were  overthrown  and  that  the  work  must  be  done  again 
or  the  conclusions  revised.  But  as  for  Gay-Lussac 
himself,  so  convinced  was  he  of  the  truth  of  the  interpre- 
tation of  Lavoisier  that  he  contented  himself  with  search- 
ing whether  the  formula  of  the  sugar,  as  determined  by 
his  perfected  method,  would  not  accommodate  itself  so  as 
to  break  up  into  alcohol  and  carbonic  acid.  This  was 
to  admit  as  exact  the  short-lived  conclusion  of  Lavoisier. 
But  the  proof  very  nearly  succeeded.  Believing  that 
Lavoisier  was  entirely  right,  Gay-Lussac  did  not  hesitate 
even  to  give  what  is  commonly  called  a  coup  de  pouce, 
and  to  modify  from  2  to  3  per  cent  the  figures  which 
his  experiment  had  given  him  in  order  to  make  them 
fit  into  the  hypothetical  outline  traced  by  Lavoisier. 
A  singular  spectacle  !  the  degree  of  confidence  and  security 
of  conscience  to  which  a  preconceived  idea  may  lead! 
A  strange  spectacle  to  see  Gay-Lussac  continue,  but 
happily  only  on  this  one  point,  the  tradition  of  those 
alchemists  of  the  middle  ages,  who  consented,  it  is  true, 
to  inquire  of  experiment,  but  who  did  not  question  it 
impartially,  and  listened  only  when  it  answered  in  ac- 
cordance with  their  desires! 

Starting  from  an  inexact  experiment,  supported  by 
the  figures  of  an  analysis  voluntarily  perverted,  the  idea 
of  Lavoisier  nevertheless  made  its  way,  because  of  its 
simplicity.  It  naturally  met  with  more  credence  when 
Dumas  and  Boullay  observed  in  1828  that  every  in- 
correct statement  in  the  interpretation  of  Gay-Lussac 
could  be  made  to  disappear  by  admitting  that  the  cane- 
sugar  assimilates  the  elements  of  a  molecule  of  water 
before  undergoing  alcoholic  fermentation.  This  inter- 
pretation, supported  by  experiment,  reestablished  both 
the  truth  of  the  idea  of  Lavoisier  and  the  accuracy  of  the 
calculations  of  Gay-Lussac  ;  it  had  only  one  thing  against 


CAGNIARD-LATOUR,    SCHWANN,    HELMHOLTZ  59 

it — it  was  entirely  a  work  of  calculation.  It  had  no 
other  foundation  than  the  experiment  of  Lavoisier  which 
was  evidently  not  exact,  and  had  not  been  the  object  of 
any  verification. 

Any  one  who  had  wished,  about  1850,  to  get  an  idea 
of  the  degree  of  credence  which  the  equation  merited,  the 
equation  of  alcoholic  fermentation  accepted  everywhere, 
would  have  been  justified  in  being  entirely  sceptical  on 
the  subject,  especially  if  he  had  asked  himself  why  all 
the  chemists  who  were  occupied  with  this  question  passed 
by  obstinately  in  silence  this  yeast  which  Lavoisier  had 
been  obliged  to  add  to  make  his  sugar  ferment,  and  with- 
out which  it  was  impossible  to  obtain  any  fermentation. 
Why  should  this  yeast,  so  necessary  in  the  experiment, 
disappear  in  its  interpretation? 


Ill 
CAGNIARD-LATOUR,  SCHWANN,  HELMHOLTZj 

This  yeast  was  known  in  the  vats  of  the  brewery  as  a 
kind  of  superficial  scum,  or  as  a  precipitate  on  the  bottom, 
a  scum  or  deposit  in  which  resided  an  occult  force.  It 
multiplied  when  introduced  into  a  sweetened  must  and 
caused  it  to  ferment:  apparently  when  it  was  not  intro- 
duced it  formed  there  spontaneously,  and  Thénard  had 
shown,  in  1803,  that  all  sugared  juices  which  ferment  of 
their  own  accord,  give  a  precipitate  having  the  external 
appearance  and  the  properties  of  the  yeast  of  beer. 

This  yeast  seemed,  therefore,  necessary  to  the  fer- 
mentation. In  an  experiment  which  perplexed  Pasteur 
too  much  for  us  to  pass  over  it,  Gay-Lussac  had  shown 
that  something  else  was  needed.  That  able  physicist 
caused  to  mount  to  the  top  of  a  test  tube  filled  with 


60  pasteur:  the  history  of  a  mind 

mercury,  some  grapes,  the  surface  of  which  had  been 
washed  many  times  with  hydrogen  in  order  to  remove 
all  traces  of  air  from  the  skins.  Then  he  had  crushed 
them  against  the  top  of  the  tube  with  the  aid  of  a  curved 
iron  rod  introduced  under  the  mercury.  No  fermenta- 
tion occurred,  which  might  appear  very  surprising  in 
view  of  the  facility  and  rapidity  with  which  fermentation 
ordinarily  takes  place  in  the  vintage.  When  it  was 
thoroughly  demonstrated  that  there  would  not  be  any, 
Gay-Lussac  brought  into  contact  with  the  crushed  grapes 
some  bubbles  of  oxygen  and  saw  fermentation  begin  in 
a  very  short  time  thereafter.  From  this  he  concluded 
that  oxygen  was  necessary  to  start  a  fermentation, 
whatever  might  be  the  rôle  of  the  yeast. 

The  experiment  is  accurate,  although  it  does  not 
always  succeed.  Gay-Lussac  tried  it  twice  and  failed 
once.  That  should  have  been  sufficient  to  make  him 
reflect  on  the  accuracy  of  his  conclusion,  but  it  was 
decreed  that,  in  this  question,  suggestion  should  play  a 
great  rôle.  Oxygen  was  then  at  the  height  of  its  glory, 
and  by  opening  to  it  the  domain  of  the  fermentations 
Gay-Lussac  not  only  acted  in  accordance  with  the  pre- 
vailing belief,  but  explained  at  the  same  time  the  pre- 
serving methods  of  Appert,  who,  in  heating  his  bottles 
and  flasks,  was  seen  to  be  driving  out  the  oxygen,  and, 
in  reality,  did  not  leave  any  of  it  behind,  as  experiment 
showed.  Gay-Lussac  explained  also  the  very  ancient 
practice  of  interrupting  fermentation  by  sulphuring  casks 
or  the  juice  of  the  grapes.  Consequently  his  interpre- 
tation has  entered  into  people's  minds,  has  remained, 
and  has  exercised  even  on  the  science  of  our  own  time  an 
unquestionable  influence. 

Hitherto,  the  question  had  been  confined  to  the  domain 
of  chemistry.  Since  Fabroni  (1799),  the  yeast,  whatever 
its  rôle,  was  considered  as  a  gluten,  and  it  did  not  occur 


CAGNIARD-LATOUR,    SCHWANN,    HELMHOLTZ  61 

to  the  mind  of  Thénard  to  consider  it  as  anything  but  a 
chemical  compound.  As  for  the  intervention  of  the 
oxygen,  that  also  was  only  chemistry.  But  at  this 
time  there  appeared  in  science  a  new  idea,  founded  on  an 
old  observation,  made  for  the  first  time  in  1680  by  Leu- 
wenhoeck,  then  by  Desmazières  in  1825,  and  renewed  in 


Fig.  7. — Top  yeast  of  beer. 
Young.  Old. 

1835,  almost  simultaneously,  in  Germany  by  Kutzing 
and  I.Schwann,  and  in  France  by  Cagniard-Latour. 
Subjecting  the  yeast  to  a  microscopical  examination,  all 
these  observers  had  seen  that  it  consisted  of  ovoid  or 
spherical  globules  of  an  organized  aspect  (Fig.  7),  which 
Cagniard-Latour  had  the  merit  to  consider  as  clearly 
living  beings,  "  Capable  of  reproducing  themselves  by 


62  pasteur:  the  history  of  a  mind 

budding,  and  probably  acting  on  sugar  only  as  a  result  of 
their  growth." 

It  was  only  a  phrase.  Schwann  had  brought  argu- 
ments and  made  experiments.  He  had  shown  in  the 
first  place  that,  contrary  to  what  Gay-Lussac  had  said, 
oxygen  was  not  sufficient  to  start  a  fermentation.  When 
heated  air  was  admitted  to  sugared  must,  the  sugar  re- 
mained intact,  and  no  yeast  was  produced.  But  the 
oxygen  in  the  air  had  not  been  touched.  That  which  was 
lacking  was  a  something  contained  in  the  air,  which  the  heat 
had  destroyed.  Schwann  says  clearly  that  this  some- 
thing is  a  germ;  he  even  says  it  is  a  vegetable  germ, 
basing  this  statement  upon  the  fact  that  he  has  found 
the  yeast  sensitive  to  arsenic,  like  many  vegetables,  and 
not  to  nux  vomica,  which  is  deadly  to  many  animals. 
He  found  the  yeast  in  the  precipitate  of  fermented  bever- 
ages ;  he  assured  himself  that  the  fermentation  begins  only 
when  the  yeast  is  present,  and  is  arrested  when  the 
yeast  ceases  to  multiply.  He  recognized  the  existence 
of  a  very  close  relation  between  the  reproduction  of  the 
yeast  and  the  fermentation,  and  in  closing,  he  expresses 
the  opinion  that  the  plant  nourishes  itself  on  the  sugar 
and  rejects  in  the  form  of  alcohol  everything  that  it 
cannot  use. 

Almost  word  for  word  this  is  a  statement  of  our 
present  ideas.  So  perfectly  do  we  agree  with  it  that 
we  ask  ourselves  why  the  contemporaries  of  Schwann 
were  not  able  to  hear  his  voice.  The  reason  is  very 
simple:  they  had  their  prejudices  as  we  surely  have  ours. 
They  also  loved  new  ideas  less  than  we;  they  demanded 
proofs  before  accepting  new  ideas,  and  it  is  unfortunate 
that  those  of  Schwann  had  not  the  desired  clearness. 
The  very  short  memoir,  in  which  they  were  set  forth, 
was  given  out  as  a  preliminary  communication,  but 
this  was  not  followed  by  any  more  detailed  publication. 


CAGNIARD-LATOUR,    SCHWANN,    HELMHOLTZ  63 

The  experiments,  when  repeated,  were  not  always 
successful,  especially  when,  instead  of  working  with 
sugared  musts,  organic  infusions  were  used.  But  how 
separate,  in  their  causes  and  origins,  phenomena  so 
evidently  analogous  as  fermentation  and  putrefaction? 
Opinion  remained,  therefore,  a  little  hesitating,  and  the 
best  proof  that  the  old  ideas  were  not  disturbed  is  the 
work  of  Helmholtz  published  in  1843,  the  first  work  of 
the  illustrious  physicist. 

Helmholtz  repeated  with  success  the  experiment 
of  Schwann,  and  asked  himself  what  is  this  something 
in  the  air  which  heat  kills,  or  renders  inactive. 
It  may  be,  he  said,  only  a  putrid  exhalation  coming 
from  a  mass  undergoing  fermentation,  and  capable, 
by  virtue  of  an  unknown  power,  of  provoking  a  new 
fermentation:  or  else  it  is  a  living  germ.  In  the  latter 
case,  the  germ  is  insoluble  in  water.  The  putrid  ex- 
halation is,  on  the  contrary,  soluble  and  therefore  dif- 
fusible. Let  us  take,  therefore,  two  vessels  separated 
by  a  membrane;  in  one  let  us  place  a  liquid  under- 
going fermentation,  or  putrefying,  in  the  other  a  liquid 
of  the  same  nature  but  not  fermenting,  and  let  us  see 
what  will  happen.  If  the  fermentation  does  not 
cross  the  membrane,  then  it  is  produced  by  living 
creatures;  if  it  does  pass  the  membrane,  it  must  be 
attributed  to  something  else. 

Now  the  experiment  is  always  successful  with  liquids 
undergoing  alcoholic  fermentation,  and  rarely  or  never 
with  macerated  meat.  That  is,  the  presence  of  the 
membrane  prevents  the  alcoholic  fermentation  from 
passing,  but  does  not  arrest  the  cause  of  putrefaction, 
whatever  it  may  be.  From  this  Helmholtz  concludes 
that  there  are  two  kinds  of  transformation  of  organic 
matter,  one  which  takes  place  with  the  concourse  of 
microscopic  organisms,  and  the  other  without  them. 


64  pasteur:  the  history  of  a  mind 

IV 
LIEBIG 

This,  then,  was  the  result  of  the  first  attempt  of  the  vital- 
istic  theory  of  fermentation  to  range  itself  as  an  opponent 
of  the  purely  chemical  theory.  Cagniard-Latour,  Helm- 
holtz,  Schwann,  were  forerunners,  but  no  one  listened  to 
them.  The  uncertainty  of  their  experiments  and  argu- 
ments accounted  for  this  to  some  extent.  There  was 
another  and  greater  obstacle,  namely,  the  general  state 
of  the  scientific  mind  of  the  time.  Chemistry  had  just 
done  such  beautiful  things,  that  it  believed  itself,  and 
every  one  believed  it,  capable  of  doing  still  more.  It 
did  its  best  to  explain  everything,  down  to  the  most 
mysterious  phenomena  of  life,  by  the  simple  play  of 
physical  and  chemical  forces,  and  behold  how,  in  a 
remote  corner  and  one  little  known  to  science,  it  sees 
reappear  in  the  form  of  an  animate  cause,  those  living 
forces  which  it  had  expelled  little  by  little  from  the 
domain  of  physiology.  That  seemed  to  it  a  step  back- 
ward. "In  what  respect,"  said  Liebig,  apparently 
with  reason,  "does  the  explanation  of  fermentation 
appear  to  you  any  clearer  when  you  have  introduced 
into  it  a  living  organism,  even  if  it  is  everywhere  in 
it  !  But  you  see  for  yourself  that  they  are  not  present 
in  the  putrefactions.  Let  us  admit,  if  you  wish, 
although  it  seems  very  extraordinary,  that  the  meat  and 
the  sugar  are  destroyed  by  different  methods.  But  the 
sugar  can  undergo  diverse  fermentations,  very  close  to 
the  alcoholic  fermentation,  and  even  frequently  accom- 
panying it:  the  lactic  fermentations,  the  butyric,  etc. 
Do  you  find  in  these  fermentations  anything  resembling 
the  yeast?  Do  they  not  behave  exactly  like  the  macer- 
ations of  meat?     Your  explanation  limps,  and  encoun- 


LIEBIG  65 

ters  obstacles  at  every  step.  For  me,  on  the  contrary, 
these  transformations  present  a  common  character, 
namely,  that  of  taking  place,  every  one  of  them,  in 
the  presence  of  an  organic  substance  in  the  process  of 
decomposition.  We  start  a  lactic  or  butyric  fermen- 
tation by  means  of  old  cheese,  or  putrid  meat.  As  for 
the  alcoholic  fermentation,  Colin  showed  in  1828,  that 
this  could  be  provoked  by  means  of  many  organic 
nitrogenous  substances,  different  from  the  yeast  of 
beer,  provided  that  they  are  in  process  of  decomposition. 
It  is  these  dead  substances  which  form  the  ferment. 
I  do  not  forget  the  experiments  of  Thénard  on  the  almost 
constant  production  of  yeast  in  juices  when  in  fermen- 
tation; I  do  not  forget,  furthermore,  the  conclusions 
of  Cagniard-Latour  and  Schwann  confirmed  by  Quevenne, 
Turpin,  and  Mitscherlich.  But  this  yeast  does  not 
embarrass  me,  it  enters  into  my  system.  If  you  admit 
that  it  lives,  then  you  admit  also  that  it  dies.  Now, 
it  is  in  dying  that  it  acts,  as  a  result  of  the  decomposition 
which  it  undergoes  at  this  moment  and  of  that  Thénard 
furnishes  us  the  proof." 

That  savant  had  seen,  in  fact,  that  by  adding  20  parts 
of  yeast  to  100  parts  of  cane-sugar  in  solution  in  water, 
he  obtained  a  rapid  and  regular  fermentation,  after 
which  the  remaining  yeast  collected  on  a  filter  weighed 
no  more  than  13.3  grams.  Added  to  a  fresh  and  equal 
quantity  of  sugar,  this  residue  produced  a  fermentation 
more  slowly  than  the  first  time,  after  which  it  was 
reduced  to  10  grams,  and  was  incapable  of  producing 
a  new  fermentation.  What  more  fitting  to  demon- 
strate that  the  yeast  destroys  itself  and  is  consumed  by 
its  own  activity?  The  theory  of  Liebig  finds  a  good 
defense,  therefore,  from  this  point  of  view.  As  for  the 
undeniable  multiplication  of  the  yeast  in  the  vat  of  the 
brewery,  in  the  manufacture  of  wine,  especially  of  the 


66  pasteur:  the  history  of  a  mind 

white  wines,  Liebig,  who  had  much  imagination,  had 
an  explanation  all  ready.  All  the  fermentable  liquids 
contain  what  he  called  gluten,  what  we  would  call  to-day 
albuminoid  substances.  In  contact  with  air  this 
gluten  oxidized  and  was  precipitated  in  the  form  of 
yeast:  this  is  the  explanation  of  the  experiment  of  Gay- 
Lussac.  Consequently,  in  proportion  as  one  part  of 
the  yeast  destroys  itself  by  acting  on  the  fermentable 
substance,  another  forms:  if  more  is  formed  than  is 
destroyed  we  have  the  case  of  the  brewery  vats;  if 
more  is  destroyed  than  is  formed,  we  have  the  case  of 
Thénard's  experiments  concerning  which  we  have  just 
spoken.    , 

For  the  fundamental  explanation  of  the  phenomena, 
Liebig  had  only  to  take  the  ideas  of  Willis  and  of  Stahl 
on  the  internal  movement  of  a  mass  in  fermentation, 
attributing  the  motive  power  to  the  ferment.  "The 
yeast  of  beer,  and  in  general  all  animal  and  plant  sub- 
stances undergoing  putrefaction,  impart  to  other  sub- 
stances the  state  of  decomposition  in  which  they  find 
themselves.  The  movement  which  is  imparted  to 
their  own  elements,  as  the  result  of  the  disturbance  of 
the  equilibrium,  is  communicated  equally  to  the  elements 
of  the  substances  which  are  found  in  contact  with  them." 
For  example,  sugar  is  a  stable  compound  with  respect 
to  a  great  number  of  external  influences,  air,  light,  even 
heat.  On  the  contrary,  it  is  an  unstable  structure  with 
respect  to  the  molecular  movement  of  organic  sub- 
stances in  decomposition:  under  their  action  it  breaks 
up  easily  into  alcohol  and  carbonic  acid. 

Thus  the  theory  of  Liebig,  without  denying  or  accept- 
ing formally  the  organization  of  the  yeast  globule, 
confined  itself  to  denying  its  vital  rôle  in  fermentation, 
and  collected  all  these  phenomena  into  one  single 
formula.     From   all   sides,   it  presented    a   good   face, 


pasteur:  lactic  fermentation  67 

and  as  it  was  defended  with  energy  and  talent,  it  ended 
by  triumphing.  Taught  in  all  the  books,  accepted  as 
true  in  all  the  works  published  on  fermentation,  it  had 
become  almost  a  dogma,  that  is  to  say,  what  in  science  is 
the  most  difficult  to  overturn.  We  may  attack  facts  by 
showing  that  they  are  inexact,  experiments  by  testing 
their  conclusions;  but  what  can  we  do  against  a  doctrine 
to  some  extent  philosophic,  resting  for  the  most  part  on 
argumentation,  an  argumentation  so  voluminous  that 
one  can  demolish  certain  parts  of  it  without  weakening 
the  rest,  and  which  is  based  on  that  half  mystical  con- 
ception of  an  imparted  movement? 

This  detailed  exposition  was  necessary  in  order 
to  show  the  state  of  the  question  at  the  time  Pasteur 
approached  it,  and  to  understand  the  nature  of  the  means 
which  he  employed  to  solve  it.  We  shall  now  be  able 
to  go  on  more  quickly:  we  have  reached  the  level  ground. 


V 
PASTEUR:  LACTIC  FERMENTATION 

The  point  which  I  wish  to  make  clear  in  the  beginning 
is  this:  if  Pasteur  immediately  made  decided  progress  in 
his  studies  it  is  because  he  approached  them  with  another 
guiding  idea  than  his  contemporaries. 

In  his  memoirs,  especially  in  the  introduction  to  his 
Mémoire  sur  la  fermentation  lactique, l  it  is  easy  to  find 
what  guided  him,  but  it  must  be  a  little  more  developed. 
Its  origin  is  an  observation  made  during  the  study  of  the 
rotary  power.  In  many  of  the  industrial  fermentations, 
we  meet,  as  a  secondary  product,  amyl  alcohol,  a  sub- 
stance endowed  with  rotary  power  and  capable,  further- 

1  Ann.  de  ch.  et  de  phys.,  3e  série,  t.  LU.     Paris,  1858,  p.  404. 


68  pasteur:  the  history  op  a  mind 

more,  of  forming  several  crystalline  combinations  which 
do  not  show  any  hemihedrism.  It  was  the  first  exception 
which  Pasteur  had  encountered  in  this  law  of  correlation 
between  hemihedrism  and  the  rotary  power.  Now,  ac- 
cording to  the  current  ideas  of  the  epoch,  fermentation 
was  a  disintegration  :  it  was  the  breaking  up  of  a  molecule 
by  decay,  the  débris  of  which,  still  voluminous,  formed 
new  mo'ecular  edifices  which  were  the  products  of  the 
fermentation.  Consequently,  by  virtue  of  the  theory 
of  Liebig,  the  edifice  of  amyl  alcohol  must  form  some 
part  of  the  framework  in  the  molecule  of  the  sugar  in 
order  to  resist  dismemberment,  and  as  it  preserves  the 
rotary  power  its  optical  action  must  be  derived  from  that 
of  sugar. 

This  idea  was  repugnant  to  Pasteur.  He  had  seen, 
for  example,  in  malic  and  maleic  acids,  that  the  least 
injury  to  the  structure  of  the  molecule  made  its  rotary 
power  disappear.  " Every  time,"  he  says,  "that  we 
try  to  follow  the  rotary  power  of  a  body  into  its  deriva- 
tives we  see  it  promptly  disappear.  The  primitive 
molecular  group  must  be  preserved  intact,  as  it  were, 
in  the  derivative,  in  order  that  the  latter  may  continue 
to  be  active,  a  result  which  my  researches  permit  me  to 
predict,  since  the  optical  property  is  entirely  dependent 
on  a  dissymmetrical  arrangement  of  the  elementary 
atoms.  But  I  find  that  the  molecular  group  of  amyl 
alcohol  is  too  far  away  from  that  of  sugar,  if  derived  from 
it,  for  it  to  retain  therefrom  a  dissymmetrical  arrange- 
ment of  its  atoms." 

The  origin  of  this  alcohol  must,  therefore,  be  more 
profound,  and,  recalling  the  before-mentioned  fact  that 
life  alone  is  capable  of  creating  full-fledged  new  dissym- 
metries, and  thinking  that  his  objection  would  no  longer 
have  a  raison  d'être,  if  between  the  sugar  and  the  amyl 
alcohol    a    living    organism    were    interposed,    Pasteur 


pasteuk:  lactic  fermentation  69 

found  himself  led  quite  naturally  to  think  of  fermenta- 
tion as  a  vital  act. 

Instinctively,  for  it  was  still  only  instinct,  he  took  his 
stand  by  the  side  of  Cagniard-Latour  and  the  vitalists. 
But,  in  order  to  defend  his  position,  it  was  necessary  for 
him  to  resort  to  experiment. 

In  collating  the  dates  of  his  different  publications,  it  is 
evident  that  he  began  at  nearly  the  same  time  the  study 
of  the  lactic  fermentation  and  the  alcoholic.  Why  did 
he  devote  his  first  work  to  the  lactic  fermentation,  a 
much  less  important  one  from  the  industrial  point  of 
view?  Without  his  telling  us,  it  is  easy  to  divine.  In 
the  first  place,  when  the  fermentation  becomes  lactic 
there  is  produced,  in  the  greatest  abundance,  this  mys- 
terious amyl  alcohol  of  which  we  have  just  spoken.  But, 
from  his  point  of  view,  there  is  another  deeper  reason, 
that  is,  that  the  alcoholic  fermentation  had  already  lost 
its  bloom.  Liebig  and  the  most  determined  of  his 
partisans  had  almost  condemned  it  by  admitting  that 
the  yeast  was  necessary,  and  that  it  might  be  a  living 
organism.  Their  great  argument,  as  we  have  said  above, 
was  always  :  what  rôle  would  you  wish  us  to  attribute  to 
the  yeast,  when  we  see  so  many  other  related  fermenta- 
tions, the  lactic  fermentation  for  example,  taking  place 
without  it,  and  without  anything  which  resembles  it? 

The  lactic  fermentation  was,  therefore,  in  a  certain 
sense,  le  champ  clos  on  which  he  must  struggle,  and  I 
believe  I  am  so  much  the  more  in  the  right  in  attributing 
to  Pasteur  this  order  of  ideas  because  his  argument  is 
confined  to  the  following:  All  that  one  does  with  the 
yeast,  I  do  with  the  grayish  deposit  which  I  find  at  the 
bottom  of  my  flasks  in  which  lactic  fermentation  is  going 
on.  The  yeast  has  an  organized  aspect  :  my  ferment  has 
also,  but  it  is  different  and  difficult  to  see,  and  you  have 
not  been  able  to  recognize  it  because,  owing  to  your  idea 


70  pasteur:  the  history  of  a  mind 

that  the  organic  matter  itself  is  the  ferment,  and  so  much 
the  more  the  ferment  the  less  it  is  disorganized,  you  take 
for  the  ferment  the  altered  gluten  and  the  rotted  cheese 
whose  amorphous  débris  covers  and  obscures  the  organ- 
ized ferment.     As  for  me,  I  have  another  idea,  accord- 


Fig.  8. — Ferments  of  wine  and  beer:  (1)  Bacillus  of  turned  wine;  (2) 
lactic  ferment;  (3)  butyric  ferment;  (4)  ferments  of  ropy  wine;  (5)  fermenta 
of  vinegar;  (6)  amorphous  deposit;  (7)  sarcina.  In  all  of  the  fields  yeast 
cells. 

ing  to  which  the  organic  matter  is  only  the  food  for  the 
ferment.  I  offer  this  food  to  it  in  a  liquid  state  in  bouil- 
lons or  clear  macerations,  and  then  my  ferment  forms, 
at  the  bottom  of  the  flasks,  a  homogeneous  layer  where  it 
exists  alone,  or  where,  when  mixed,  one  can  dissolve  with 


pasteur:  lactic  fermentation  71 

a  little  acid  the  carbonate  of  lime  which  I  have  had  to 
add  to  it.  And  then  it  is  easy  to  observe  it  and  to  recog- 
nize it  as  an  organized  being,  all  the  individuals  of  which 
resemble  one  another. 

Furthermore,  this  ferment  reproduces  itself.  Just 
make,  as  I  did,  a  clear  must  containing  sugar  and  chalk: 
sow  there  a  trace  of  the  deposit  from  a  former  fermenta- 
tion, as  small  an  amount  as  you  wish,  and  you  will  see 
a  new  fermentation  begin.  The  lactic  ferment  will 
multiply,  as  does  the  yeast  of  beer.  You  will  have  more 
of  it  than  you  sowed,  and  with  this  deposit  you  will  be 
able  to  start  in  different  liquids  as  many  lactic  fermen- 
tations of  sugar  as  you  wish,  provided  these  liquids  are 
well  chosen,  for  this  ferment,  being  a  living  creature,  has 
its  special  requirements  and  develops  well  only  when  it 
finds  within  reach  all  that  it  needs. 

On  the  other  hand,  when  this  is  the  case,  it  accom- 
plishes with  rapidity  the  transformation  over  which  it 
presides.  "The  purity  of  a  ferment,  its  homogeneity, 
its  free  unrestrained  development  by  the  aid  of  food 
substances  well  adapted  to  its  individual  nature,  these 
are  some  of  the  essential  conditions  for  good  fermenta- 
tion." Here  we  have,  let  us  say,  in  our  turn,  a  revolu- 
tionary phrase,  one  that  goes  out  to  meet  the  enemy, 
drums  beating  and  fuse  lighted. 

There  is  still  more  in  this  short  memoir  of  15  pages. 
There  is  a  very  exact  statement  of  the  good  or  bad 
influence,  as  the  case  may  be,  of  the  acidity  or  alkalinity 
of  the  liquid.  The  yeast  prefers  sugared  media  which 
are  acid;  the  lactic  ferment,  neutral  sugared  media,  and 
ti  is  for  that  reason  we  add  to  the  cultures  carbonate  of 
ilme.  There  is  also  a  hint,  as  it  were  an  apparition, 
of  the  effect  of  antiseptics.  "The  essential  oil  of  onion 
juice  inhibits  completely  the  formation  of  the  yeast 
of  beer:  it  appears  equally  harmful  to  Infusoria.     It 


72  pasteur:  the  history  of  a  mind 

can  arrest  the  development  of  these  organisms  without 
having  any  notable  influence  on  the  lactic  ferment." 
Thus  one  could  use  antiseptics,  with  a  suitable  culture 
medium,  for  separating  the  ferments  one  from  another. 
This  memoir  then  is  full  of  suggestion,  and,  strangely 
enough,  all  these  propositions  which  were  so  new  and  so 
bold  for  the  epoch  were  announced  de  piano,  almost 
carelessly,  with  the  tranquil  confidence  of  a  man  sure 
of  his  facts,  and  to  whom,  if  one  did  not  known  him,  one 
might  even  have  attributed  malicious  intentions,  he 
showed  so  much  apathy.  It  is  only  at  the  end  of  his 
memoir  that  he  admits  that  nothing  of  all  this  has  been 
demonstrated.  "If  any  one  should  say  to  me  that 
in  my  conclusions  I  go  beyond  the  facts,  I  would  reply 
that  that  is  true  in  this  sense  that  I  have  taken  my 
stand  unreservedly  in  an  order  of  ideas  which,  strictly 
speaking,  cannot  be  irrefutably  demonstrated."  But 
his  system  is  so  logical  that  he  takes  pleasure  in  believing 
in  it.  Everything  is  so  consistent  in  his  conception 
and  in  his  mode  of  exposition.  The  idea  of  a  specific 
ferment  associated  with  each  fermentation,  of  dispro- 
portion between  the  weight  of  the  ferment  produced 
and  the  weight  of  the  matter  transformed,  of  vital 
competition  between  two  organisms  which  simultaneously 
invade  the  same  medium  and  ultimately  leave  it  to  the 
one  which  is  best  adapted  to  the  conditions  it  finds  there, 
— all  these  ideas,  which  the  future  was  to  develop  so  far, 
are  found  not  in  embryo,  but  clearly  set  forth  in  this 
paper,  the  work  of  exuberant  youth,  in  which  we  still 
see  the  thought  bubbling  and  fermenting.  Pasteur 
ended  it  with  a  general  profession  of  faith:  "It  is  now 
my  opinion,"  he  said,  "as  the  result  of  the  knowledge 
I  have  gained  on  this  subject,  that  whoever  will  judge 
impartially  the  results  of  this  work  and  those  which  I 
shall  publish  in  the  near  future,  will  recognize  with  me 


ALCOHOLIC   FERMENTATION  73 

that  fermentation  is  correlative  with  life,  with  the  or- 
ganization of  globules,  not  with  the  death  or  putrefaction 
of  these  globules,  neither  does  it  appear  to  be  a  phenom- 
enon of  contact  where  the  transformation  of  the  sugar 
takes  place  in  the  presence  of  the  ferment  without 
giving  anything  to  it  or  taking  anything  from  it.  These 
latter  affirmations,  one  will  soon  see,  are  contradicted  by 
experiment." 

This  was  the  announcement  of  the  memoir  on  alcoholic 
fermentation,  to  which  we  are  now  come. 


VI 

ALCOHOLIC  FERMENTATION 

In  the  memoir  on  alcoholic  fermentation1  the  move- 
ments and  the  tone  differ  wholly  from  those  of  the 
memoir  which  precedes.  The  latter  is  not  that  tranquil 
and  almost  ironical  exposition  of  a  new  theory  which 
holds  up  its  head  and  marches  along  easily  over  a  land 
where  its  competitors  hobble  and  stumble,  or  where 
they  have  need  at  every  step  of  what  Victor  Hugo  would 
have  called  crutch  hypotheses.  It  is  a  series  of  blows 
straight  from  the  shoulder,  delivered  with  agility  and 
assurance. 

Ah!  You  insist  on  thinking  of  alcoholic  fermentation 
as  a  simple  breaking  up  of  sugar  into  alcohol  and  carbonic 
acid  !  Undeceive  yourselves  :  there  are  also  glycerin  and 
succinic  acid  formed  in  considerable  quantities  and  almost 
as  constantly  as  the  principal  products  of  the  fermentation. 

Ah!  So  you  are  bound  to  ignore  the  yeast  in  this 
phenomenon,  or  at  the  most  will  concede  to  it  only  the 
rôle  4of  an  initiator  !  Very  well  !  Learn  that  this  yeast 
1  Ann.  de  ch.  et  de  phys.,  3«  série,  t.  LVIII,  1860. 


74  pasteur:  the  history  of  a  mind 

always  borrows  something  from  the  sugar,  and  makes 
a  part  of  its  own  tissues  out  of  this  food.  Learn  also 
that  it  is  only  on  the  condition  of  keeping  a  little  of  the 
sugar  for  itself,  that  it  consents  to  give  you  the  rest  in 
the  form  of  alcohol. 

Ah!  Do  you  believe  that  you  can  write  an  equation 
for  the  alcoholic  fermentation  as  you  write  the  equation 
for  the  preparation  of  oxygen?  Very  well!  Simply 
to  account  for  the  production  of  the  glycerin  and  the 
succinic  acid,  the  equation  must  be  very  complicated, 
and  if  you  wish  to  take  into  consideration  the  things 
borrowed  by  the  yeast  from  the  sugar,  it  will  become  so 
complex  that  it  would  be  better  not  to  write  it  at  all. 
Would  you  dream  of  writing  in  the  form  of  an  equation 
the  series  of  transformations  which  are  undergone  by 
the  sugar  in  the  tea  or  coffee  you  drink?  The  yeast  is  a 
living  thing  just  as  you  are. 

This  is  a  résumé  of  the  attack  directed  by  Pasteur 
against  the  old  ideas,  and  when  he  had  demolished  them, 
he  set  about  their  reconstruction.  Omitting  some  of 
the  less  important  details,  and  taking  up  the  exposition 
proper,  the  edifice,  it  must  be  admitted,  is  simple:  it 
amounted  to  this,  to  produce  regular  fermentation  under 
conditions  in  which  none  of  the  prevailing  theories  could 
explain  the  phenomenon. 

It  is  curious  to  see  how  the  idea  of  this  pertinent  ex- 
periment came  to  Pasteur  little  by  little. 

Thénard,  we  have  seen,  had  determined  that  there  was 
a  diminution  in  the  weight  of  the  yeast  during  fermen- 
tation, which  is  true  for  the  conditions  of  his  experiment. 
He  had  found,  furthermore,  that  this  yeast,  when  ex- 
hausted in  the  presence  of  an  excess  of  sugar,  no  longer 
contained  nitrogen.  This  last  was  an  error,  due  to  the 
imperfection  of  the  methods  in  use  for  the  detection  of 
this  substance. 


ALCOHOLIC   FERMENTATION  75 

On  this  first  error,  Dôbereiner  grafted  another  by 
affirming  that  the  nitrogen  lost  by  the  yeast  was  found 
in  the  fermented  liquid  in  the  state  of  ammonia.  As 
organic  matters  in  decomposition  also  produce  ammonia, 
this  affirmation  of  Dôbereiner  was,  clearly,  very  favorable 
to  the  ideas  of  Liebig,  and  the  latter,  a  great  collector 
of  facts  and  abstractor  of  quintessence,  did  not  fail  to 
seize  on  this  and  make  it  serve  to  prop  his  doctrine  of 
fermentation. 

For  Pasteur,  on  the  contrary,  this  fact  was  inexplicable, 
since  the  ferment  was  not  a  dead  substance  in  process  of 
destruction,  but  a  living  thing  in  process  of  organiza- 
tion. In  trying  to  discover  whether  the  statement  of 
Dôbereiner  was  true  he  found  not  only  that  the  nitrogen 
of  the  yeast  did  not  leave  it  in  the  form  of  ammonia, 
but,  moreover,  that  the  yeast  in  process  of  fermentation 
caused  the  ammonia  to  disappear  from  ammoniacal 
salts  added  to  the  liquid. 

But  how  could  the  yeast  do  this?  He  then  was  very 
bold  to  reverse  the  reasoning  of  Liebig  and  of  Dôber- 
einer, and  to  say:  the  albuminoid  substance  of  the  fer- 
ment does  not  give  up  ammonia;  it  is,  on  the  contrary, 
the  ammonia  which  produces  the  albuminoid  substance. 

This  way  of  looking  at  it  was  so  new  and  the  pre- 
sumption seemed  so  ill-founded  that  Pasteur  hesitated, 
as  he  himself  acknowledges.  But  it  was  in  accordance 
with  facts  and  the  logic  of  his  ideas.  In  any  case,  the 
only  thing  to  do  was  to  resort  to  experiment.  After 
some  attempts,  the  latter  succeeded,  and  it  became  the 
critical  experiment,  the  experimentum  crucis,  which 
made  it  possible  to  judge  the  doctrines  side  by  side. 

This  experiment  was  entirely  new.  The  problem  was 
to  grow  the  yeast  in  a  liquid  deprived  of  all  organic 
nitrogenous  matter — one  containing  only  perfectly  pure 
cane-sugar,  various  mineral  salts  to  supply  the  yeast 


76  pasteuk:  the  history  of  a  mind 

globules  with  the  elements  of  their  structure,  and  an 
ammonia  salt  to  provide  them  with  nitrogen.  If,  in 
this  medium,  completely  robbed  of  that  organic  nitrog- 
enous matter  which  Liebig  declared  to  be  necessary, 
one  obtains  a  fermentation,  and  if,  at  the  same  time, 
the  yeast  multiplies  and  develops,  deriving  all  the 
complex  elements  for  its  tissues  from  the  sugar  and  the 
ammonia,  it  will  certainly  be  impossible  not  to  admit 
a  correlation  between  the  fermentation  and  a  phe- 
nomenon of  development  and  of  life  in  this  ferment 
which  Liebig  considered  a  dead  substance. 

With  the  same  blow  by  which  the  theory  of  Pasteur 
triumphed  there  fell  into  ruin  not  only  the  theory  of 
Liebig,  but  another  theory  then  much  less  nourishing, 
namely  that  of  Berzélius,  according  to  which  the  ferment 
exerted  an  action  only  by  its  presence,  and  provoked 
the  decomposition  of  the  organic  matter  without  deriving 
anything  from  it  or  contributing  anything  to  it,  remain- 
ing, furthermore,  unchanged  in  quantity  and  quality 
throughout  the  process.  In  our  experiment,  the  ferment 
must,  on  the  contrary,  increase  in  weight,  taking  all  this 
increase  from  the  sugar. 

It  is  just  because  this  experiment  was  so  interesting 
that  it  Was  difficult.  It  was  necessary,  in  the  first  place, 
for  Pasteur  to  devote  his  attention  to  supplying  the 
yeast  with  a  suitable  mineral  medium,  and  a  rather  com- 
plex one  too,  including  phosphates,  salts  of  potassium, 
magnesium,  and  ammonia.  It  matters  not  that  the 
cell  of  the  yeast  is  small  ;  its  needs  are  great  and  varied. 
It  was  the  first  time  that  Pasteur  had  run  up  against  its 
exacting  requirements,  and  the  lesson  which  he  drew 
from  this  contact  was  not  lost.  Furthermore,  even  when 
one  gives  to  the  yeast  all  that  it  needs  in  the  way  of 
mineral  substances,  it  has  much  more  difficulty  in  living 
in  this  medium  where  it  must  form  all  the  substances 


ALCOHOLIC    FERMENTATION  77 

constituting  its  tissues,  than  in  the  juice  of  the  grape  or 
the  must  of  beer  where  it  finds  everything  composed  of 
utilizable  elements.  Nevertheless,  in  his  Mémoire  sur  la 
fermentation  alcoolique  Pasteur  succeeded  in  giving  an 
example  of  fermentation  accomplished  under  these 
difficult  conditions. 

Later,  feeling  the  importance  of  this  experiment,  he 
returns  to  it,  perfects  it,  and  renders  it  surer  by  em- 
ploying a  more  vigorous  yeast  than  that  of  his  first 
experiments.  It  is  scarcely  13  years  later  in  his  Etudes 
sur  la  bière  that  he  gives  it  the  definitive  form.  But  what 
he  says  in  his  memoir  of  1860  is  sufficient  to  carry 
conviction. 

No,  it  is  not  true,  he  said  in  substance,  that  there  is 
need  of  organic  material  in  decomposition  in  order  to 
start  alcoholic  fermentation.  An  imperceptible  trace 
of  yeast,  introduced  into  a  liquid  containing,  in  addition 
to  the  pure  sugar,  only  pure  crystallized  mineral  salts, 
makes  this  sugar  ferment  and,  at  the  same  time,  the 
yeast  develops,  buds  and  multiplies.  All  the  carbon 
of  the  new  globules  is  derived  from  the  sugar,  all  their 
nitrogen  from  the  ammonia,  which  destroys  also  the 
theory  of  Berzélius,  according  to  which  the  ferment 
acts  only  by  its  presence,  in  the  same  way  that  a  red- 
hot  cannon-ball  would  start  a  fire.  Moreover,  it  is  not 
simply  in  the  absence  of  already  manufactured  organic 
nitrogenous  matter  that  the  yeast  globules  borrow  from 
the  sugar  what  they  need  :  on  the  contrary,  there  is  every 
indication  that  this  borrowing  follows  exactly  the  same 
laws  when  the  liquid  is  more  favorable  to  fermentation. 

There  is,  nevertheless,  a  difference,  namely  that  in 
those  rich  liquids,  the  musts,  the  new  globules  which 
form,  finding  themselves  surrounded  by  nutrient  sub- 
stances, have  no  need  of  borrowing  anything  from  the 
globules  already  formed,  while  in  an  exhausted  medium 


78  pasteur:  the  history  of  a  mind 

such  as  sugared  water,  the  new  globules  live  at  the  ex- 
pense of  substances  which  the  older  globules  have 
allowed  to  diffuse  into  the  liquid.  All  are  famished  and 
then  the  young  consume  the  old.  It  is  this  work  of 
diffusion  and  of  exhaustion  of  globules  already  formed 
in  order  to  feed  the  young,  which  caused  the  diminishing 
weight  of  the  yeasts  sown  by  Thénard  in  the  sugared 
water  in  the  experiments  cited  above,  and  which  has 
led  to  the  belief  that  the  yeast  is  destroyed  in  fermenting 
the  sugar.  In  reality,  there  were  not  enough  of  the 
new  globules  formed  to  compensate  for  the  loss  of  weight 
which  the  old  globules  underwent  as  the  result  of  the 
diffusion  but  if  we  add  to  the  weight  of  the  globules  the 
weight  of  the  soluble  organic  matter  which  the  filter  does 
not  retain,  but  which  we  can  find  and  estimate  in  the 
liquid,  we  see  that  this  total  weight  always  increases 
during  the  fermentation,  because  there  is  always  a  little 
sugar  which  becomes  yeast. 

In  proportion  as  the  fermentation  is  accomplished 
under  better  conditions  and  the  yeast  is  less  exhausted 
toward  the  end,  the  increase  in  weight  is  more  notable. 
We  are  aware  of  this  from  the  fact  that  the  yeast  con- 
tinues to  give  off  carbonic  acid  at  the  expense  of  its  own 
tissues  for  some  time  after  all  the  sugar  has  disappeared 
from  the  liquid  which  bathes  it.  We  would  say  to-day 
that  it  consumes  the  reserve  food  which  it  has  made, 
for  it  is  a  provident  little  cell  which  stores  up  in  a  time 
of  plenty  for  a  time  of  famine.  How  is  it  possible  not  to 
see  that  all  this  is  a  question  not  of  decomposition  and 
of  death,  but,  on  the  contrary,  of  development  and 
of  life? 


AEROBIC   LIFE   AND   ANAEROBIC   LIFE  79 

VII 
AEROBIC  LIFE  AND  ANAEROBIC  LIFE 

And  Pasteur,  in  all  the  enthusiasm  of  his  discovery, 
adds  or  did  add  soon:  It  is  not  simply  for  alcoholic 
fermentation  that  this  is  true.  I  can  return  now  to 
affirmations  respecting  the  lactic  fermentation,  which 
it  is  very  easy  to  start  in  a  purely  mineral  medium. 
The  lactic  ferment  is  smaller  and  in  appearance  simpler 
than  the  alcoholic  ferment.  It  is  a  little  cell  constricted 
in  the  middle  (2,  Fig.  8)  and  the  whole  interior  of  which 
is  filled  with  a  mass  that  appears  to  be  homogeneous, 
whereas  it  is  differentiated  in  the  yeasts.  But  the  needs 
of  this  little  cell  are  not  less:  they  are  different,  that  is 
all.  These  two  dissimilar  ferments  are,  moreover, 
specific,  that  is  to  say  the  alcoholic  ferment  does  not 
produce  lactic  acid,  contrary  to  what  is  generally  be- 
lieved and  taught,  and  the  lactic  ferment  does  not  yield 
alcohol  when  it  is  alone  and  unmixed  with  the  alcoholic 
ferment. 

Do  not  believe,  furthermore,  with  Boutron  and  Frémy, 
that  successive  fermentations  can  take  place  in  the  same 
medium  with  or  without  order,  according  to  the  mode 
and  progress  of  the  decomposition  of  the  nitrogenous 
substance.  That  happens  when  your  spoiled  meat  or 
rotted  cheese  carries  with  it  into  the  fermentation  flask 
the  numerous  organisms  which  ordinarily  populate  it: 
it  does  not  happen  when  you  grow  a  pure  ferment  in 
clear  nutrient  bouillons.  You  are  told  that  the  butyric 
fermentation;  the  mannitic,  etc.,  accompany  or  follow 
lactic  fermentation.  It  is  not  so,  everything  stops  in 
my  flasks  when  all  the  sugar  is  transformed  into  lactic 
acid,  now  become  lactate  of  lime  by  contact  with  car- 
bonate of  lime  introduced  into  the  liquid. 


80  pasteur:  the  history  of  a  mind 

But,  while  keeping  them  separate,  we  can  make  these 
fermentations  follow  each  other,  although,  according  to 
the  ideas  of  Liebig,  they  are  interblended.  Take  this 
liquid  in  which  the  lactic  ferment  has  grown,  and  in 
which  there  are  only  lactate  of  lime  and  mineral  salts 
in  solution:  after  having  heated  it  to  sterilize  it,  sow 
there  a  drop  of  a  liquid  in  which  there  has  occurred 
spontaneously  a  butyric  fermentation,  and,  therefore, 
one  which  is  almost  surely  impure.  Phenomena  anal- 
ogous to  those  of  alcoholic  fermentation  occur:  a  gas  is 
liberated  which  is  no  longer  a  pure  carbonic  acid,  but  a 
mixture  of  this  gas  and  hydrogen.  This  mixture  has 
very  little  odor,  because  of  the  absence  of  sulphuretted 
hydrogen.  These  are  the  indications  of  a  fermentation. 
Let  us  see  now  what  is  present  in  the  liquid  which  has 
become  clouded.  We  find  there  only  motile  rods,  very 
agile,  with  undulating  movements,  sometimes  ranged  in 
a  series,  like  a  string  of  boats,  and  then  motile  on  their 
articulations  (Fig.  8,  sec.  3),  which  testifies  to  the  fact 
that  they  reproduce  and  multiply  by  elongating  and 
segmenting  across  their  longer  axis;  this  is  the  mode  of 
reproduction  called  fission. 

When  he  observed  for  the  first  time  those  organisms 
which  he  called  vibrios,  Pasteur  had  a  great  surprise, 
the  trace  of  which  is  visible  in  his  note  on  this  subject. 
The  yeast  of  beer  and  the  lactic  ferment  were  non-motile 
globules;  the  butyric  ferment  was  motile,  and  partook 
of  the  nature  [animal]  of  those  organisms  which  Ehren- 
burg  and  Du  jardin  had  found  in  infusions.  O  the  power 
of  words!  Nothing  was  more  natural  than  to  find  in 
fermentations  the  same  organisms  as  in  infusions,  since 
Pasteur  nourished  his  ferments  with  vegetable  infusions; 
he  hesitates,  however,  on  finding  that  the  butyric  ferment 
belongs  to  the  Infusoria.  "I  was  so  far,  "  he  said,  "from 
expecting  such  a  result,  so  far,  indeed,  that  for  a  long 


AEROBIC   LIFE    AND   ANAEROBIC   LIFE  81 

time  I  thought  it  my  duty  to  apply  all  my  efforts  to 
dispelling  the  apparition  of  these  little  animals,  from  the 
fear  lest  they  nourished  themselves  on  the  vegetable 
ferment  which  I  supposed  to  be  the  butyric  ferment,  and 
which  I  was  trying  to  discover  in  the  liquid  medium  that 
I  employed.  But  not  able  to  find  the  origin  of  the  bu- 
tyric acid,  I  ended  by  being  struck  with  the  coincidence 
which  my  analyses  showed  me  to  exist  between  this  acid 
and  the  Infusoria,  and,  reciprocally,  between  these 
Infusoria  and  the  production  of  this  acid.  We  must 
consider  them  the  true  butyric  ferment." 

Thus  Pasteur's  surprise  came  from  the  intervention  in 
a  fermentation  of  an  organism  which  he  considered  to  be 
an  animal  because  it  was  motile,  while  the  non-motile 
alcoholic  and  lactic  ferments  were  considered  as  vege- 
tables. We  can  to-day  scarcely  understand  this  aston- 
ishment and  these  scruples.  But  from  1850  to  1860,  the 
old  barriers  established  between  the  vegetable  and  animal 
world  had  scarcely  begun  to  fall.  Although  admitting 
in  his  Recherches  sur  les  zoospores  des  algues,  which 
appeared  in  1851,  that  the  green  Infusoria  and  the  Vol- 
vocaceae  "  present  animal  characters  too  pronounced  and 
too  permanent  for  it  to  be  possible  to  relegate  them  to 
the  vegetable  kingdom,  "  de  Thuret  insists,  none  the  less, 
on  the  difficulty  of  tracing  an  exact  line  of  demarcation 
between  animals  and  the  lower  vegetables.  "At  this 
time,"  writes  my  excellent  confrère,  M.  Bornet,  "motility 
appeared  to  be  so  evidently  an  animal  character  that 
Rabenhorst  published,  between  1849  and  1852,  a  collec- 
tion of  Diatoms  and  Desmids  as  Ein  Beitrag  zur  Fauna 
von  Deutschland."  Pasteur,  who  was  not  a  naturalist, 
was  excusable  for  still  holding  this  opinion  in  1862,  and 
although  astonished  at  his  scruples,  one  must  be  pleased 
with  him  for  taking  so  much  pains^  to  efface  them  from 
his  mind.     He  did  not  suspect  then  that  this  discovery 


82  pasteur:  the  history  of  a  mind 

would  open  a  new  world,  the  world  of  the  bacteria,  a 
world  still  more  active  and  more  densely  populated  than 
the  world  of  the  yeasts. 

There  was,  in  this  same  Note  which  we  are  analysing, 
a  fact  much  more  important  than  the  animal  or  plant 
character  of  the  butyric  vibrio:  namely,  that  this  organ- 
ism lives  in  the  absence  of  the  oxygen  of  the  air  and  even 
fears  its  contact.  Pasteur  has  often  related  how  this 
fact  leaped,  so  to  speak,  into  his  field  of  vision.  In 
examining  these  liquids,  he  would  take  a  drop,  place  it  on 
the  slide,  cover  it  quickly  with  a  cover  glass,  which 
spread  it  out  in  a  flat  layer,  and  put  the  preparation 
under  his  microscope.  But  on  examining,  with  the 
care  which  he  applied  to  everything,  one  of  these  little 
flattened  drops  of  liquid  undergoing  butyric  fermenta- 
tion, he  was  astonished  to  see  that  on  the  margins  of  the 
little  drop,  wherever  it  was  in  contact  with  the  air,  the 
bacteria  had  become  non-motile  and  inert,  although  they 
continued  to  move  with  agility  in  the  central  portions. 
This  was  a  spectacle  quite  the  reverse  of  that  which  he 
had  had  occasion  to  observe  often  in  the  case  of  the 
animalcules  of  the  infusions.  Especially  when  we  ex- 
amine, under  the  microscope,  those  from  the  surface  of 
infusions,  they  voluntarily  leave  the  central  portions  of 
the  drop  to  approach  the  margin,  the  only  place  where 
there  is  enough  oxygen  for  all.  In  the  presence  of  this 
observation,  Pasteur  asked  himself  immediately:  is  it 
true  that  these  vibrios  are  trying  to  escape  from  the 
oxygen?  An  experiment  along  this  line  was  easy  to 
make.  By  passing  a  current  of  air  through  a  flask  in 
which  the  butyric  fermentation  was  going  on,  the  fermen- 
tation was  retarded  or  arrested,  and  behold  a  new  idea 
was  introduced  into  science,  the  idea  of  anaerobic  life 
as  opposed  to  aerobic  life  which  was  believed  to  be  that 
of  all  the  animals  of  creation.     We  shall  see  how  Pasteur 


AÉROBIC   LIFE   AND    ANAEROBIC   LIFE  83 

developed  this  idea  later.  For  the  moment  we  may 
content  ourselves  with  saluting  its  dawn. 

This  idea  has,  nevertheless,  an  indispensable  com- 
plement which  we  can  and  must  give  immediately. 
There  is  oxygen  everywhere,  in  the  air  and  in  the  water. 
It  is  in  the  liquid  in  which  we  have  sown  our  bacillus 
which  is  unable  to  bear  the  air,  our  anaerobic  vibrio. 
How  is  it  that  it  can  develop  in  this  aerated  medium? 
It  is  because  we  have,  unawares,  sown  with  it  in  the  liquid 
some  aerobic  organisms  which  have  consumed  its  oxygen, 
and,  this  being  achieved,  have  fallen  inert  to  the  bottom, 
permitting  the  butyric  vibrio  to  take  possession  of  the 
medium.  If  the  liquid  is  in  contact  with  the  air  some 
of  these  aerobic  organisms  have  remained  on  its  surface. 
There  they  continue  to  live,  to  swarm,  and  they  form  a 
gelatinous  layer  which  is,  for  the  oxygen,  a  barrier  as 
impermeable  as  a  wall  of  glass;  all  of  it  that  is  able 
to  penetrate  is  absorbed  in  the  passage,  and,  thanks  to 
this  aerobic  life  on  the  surface,  the  anaerobic  life  can 
pursue  its  course  in  the  depths  without  hindrance . 

Having  come  to  this  simple  and  satisfactory  concep- 
tion, it  was  not  the  moment  for  him  to  stop.  Up  to 
this  time  we  have  observed  only  the  phenomena  of  the 
fermentation  of  sugar,  or  of  the  lactate  of  lime.  Let 
us  now  turn  our  attention  to  an  albuminoid  substance, 
beef  bouillon,  egg  albumen,  meat  macerated  in  water. 
Let  us,  as  we  have  done  hitherto,  begin  the  operation 
by  introducing  into  it  a  drop  of  an  organic  liquid  under- 
going putrefaction:  we  shall  see  the  same  phenomena 
begin  again.  There  is  formed  once  more  on  the  surface 
of  our  liquid  a  living  layer  which  will  absorb  the  oxygen 
and  will  leave  the  interior  of  the  mass  free  for  the 
anaerobic  life.  If  our  liquid  is  contained  in  a  closed 
flask,  one  or  several  aerobic  generations  will  dispel 
the  oxygen,  and  will  leave  the  field  free  to  the  anaerobes. 


84  pasteur:  the  history  of  a  mind 

There  will  be  produced  once  more  the  gases,  which  this 
time  will  have  an  odor,  because  in  this  reducing  medium, 
hydrogen  is  mixed  with  sulphuretted  and  phosphoretted 
hydrogen,  which  are  not  formed  in  contact  with  air, 
or,  if  formed,  are  oxidized  immediately  :  we  shall  have, 
therefore,  a  putrid  odor.  But  the  gases  will  have  the 
same  origin  as  in  the  fermentation  of  lactate  of  lime. 
Fermentation  and  putrefaction  are  synonymous  terms, 
and  there  is  no  reason  for  maintaining  the  old  distinction, 
which  had  not  yet  disappeared  from  the  conclusions  of 
Helmholtz.  In  these  two  phenomena  the  liberation  of 
gases  has  the  same  origin,  and  it  is  due  to  organisms 
living  in  the  absence  of  air.  It  is  opportune  to  ask 
if  there  is  not  a  close  relation  between  the  phenomena 
of  fermentation  and  of  anaerobic  life.  Here  we  have  a 
great  question  which  Pasteur  put  to  himself  immediately, 
but  which  he  did  not  solve  until  some  years  after. 

I  have  thought  best  to  present  without  detailed  exami- 
nation all  these  deductions,  because  in  reality  they  were 
the  work  of  some  weeks  of  labor  and  meditation,  and 
also  because  we  have  in  them  an  example  of  Pasteur's 
insight,  of  his  ability  to  discover  and  state  a  problem, 
of  the  patience  with  which  he  gathered  together  the 
elements  of  the  solution.  During  the  best  years  of  his 
life,  this  man  lived  in  advance  of  his  time,  a  pioneer  lost 
in  the  solitude,  absorbed  in  the  contemplation  of  the 
vistas  which  he  was  discovering,  and  which  his  eye  alone 
was  to  scrutinize  and  survey.  What  less  astonishing 
than  his  apparent  indifference  to  things  of  daily  life! 
He  lived  in  his  thoughts  without  being  a  dreamer,  for  a 
dream  which  goes  somewhere  and  which  bears  fruit  is  no 
longer  a  dream. 


THIRD  PART 
Spontaneous  Generations 

I 
SPONTANEOUS  GENERATION  AND  FERMENTATION 

Pasteur's  contributions  to  the  study  of  fermentations, 
which  we  have  just  seen  going  on  under  our  eyes,  may 
be  summed  up  in  a  few  words.  Fermentation  is  no 
longer  a  vague  transformation,  indeterminate  in  its 
cause  and  in  its  origins,  capable  of  taking  place  under 
the  influence  of  any  organic  substance  whatsoever:  it 
is  a  specific  phenomenon,  due  also  to  the  existence  and 
development  of  a  specific  organism,  the  study  of  which 
under  the  microscope  is  facilitated  in  proportion  as 
we  remove  from  the  liquid  undergoing  fermentation 
those  insoluble  organic  substances  which  it  was  formerly 
believed  necessary  to  add  to  it.  Since,  by  working 
with  a  clear  bouillon,  it  is  possible  to  follow  closely 
the  organism  sown,  and  to  be  sure  that  the  bouillon 
contains  this  and  this  alone,  the  study  of  its  nutrition 
becomes  easy.  Now,  by  acting  on  the  nutrition  of  an 
organism,  we  become  the  master  of  it;  we  can  sow  it  and 
cultivate  it  with  as  much  certainty,  and  with  the  same 
absence  of  weeds,  as  we  can  lettuce  in  a  garden.  We 
can  also  banish  it  from  liquids  where  there  is  no  occasion 
for  its  presence.  In  short,  this  infinitely  small  organism 
becomes  tangible  and  open  to  experiment:  a  capital 
idea,  which  the  whole  life  of  Pasteur  will  henceforth  be 
spent  in  developing. 

Nevertheless,  the  logic  of  his  studies  placed  before  him 

85 


86  pasteue:  the  history  of  a  mind 

a  question  which,  with  just  reciprocity,  these  same  studies 
permitted  him  to  solve.  Whence  come  the  ferments? 
Are  they  organized  spontaneously  at^the  expense  of 
dead  organic  matter?  Or,  do  they  come  in  the  regular 
ways  from  organisms  like  themselves,  and  from  pre- 
existing germs?  Here  we  have  a  question  which  had 
been  asked  very  often,  ever  since  men  had  begun  to  reflect, 
and  which  had  been  solved  in  very  di%rejxt  ways. 
Pasteur,  himself,  at  the  close  of  his  studies  on  crystallog- 
raphy, had  been  very  undecided,  and  I  thinjjs:  also  very 
indifferent  regarding  the  answer.  He  had  vno  precon- 
ceived ideas:  he  would  accept  the  results  of  expeijji^^ 
mentation.  But  at  the  point  to  which  the  study  of 
fermentations  had  led  him,  he  could  no  longer  believe 
in  spontaneous  generation:  it  is  too  far  removed  from 
the  idea  of  specificity,  which  he  had  just  introduced 
into  science.  Everywhere  around  us  the  idea  of 
species  accompanies  the  idea  of  continuance  by  the 
germ  cell,  and  it  would  be  very  astonishing  if  this  order 
were  changed  in  the  world  of  the  infinitely  little. 

The  ancients  believed  in  the  spontaneous  generation  of 
eels  from  the  ooze  of  rivers,  and  in  that  of  bees  in  the 
entrails  of  a  dead  bull.  But  these  were  the  ideas  of  a 
child  who  had  never  lived  in  the  face  of  the  progress  of 
knowledge.  For  a  long  time  people  had  believed  in  the 
spontaneous  generation  of  worms  in  putrefying  meat, 
because  in  this  case  the  experiment  is  more  difficult  or 
the  observation  is  more  delicate,  and  a  Redi  was  neces- 
sary to  demonstrate  that  these  worms  come  from  eggs 
laid  by  flies,  and  that  one  would  no  longer  see  them  in  a 
piece  of  meat  which  was  protected  by  a  simple  layer  of 
gauze.  It  is  true  that  this  piece  of  meat  continued  to 
putrefy,  to  decay,  and  to  nourish,  no  longer  worms  but 
confused  tribes  of  microscopic  organisms.  As  long  as 
it  was  the  belief  that  fermentation  and  putrefaction  oc- 


BUFFON,    NEEDHAM,    SPALLANZANI,   ETC.  87 

curred  by  chance,  without  any  order  or  regulation,  it 
had  been  possible  to  believe  that  the  organisms  which 
accompanied  them  were  also  due  to  the  spontaneous 
organization  of  the  elements  of  the  meat  undergoing 
putrefaction,  or  of  the  organic  matter  added  to  the 
liquids  of  fermentation.  But  as  soon  as  these  fermenta- 
tions and  the  organisms  which  produced  them  assumed 
something  of  a  spécifie  nature,  there  was  something 
strange  in  making  them  come  into  existence  spon- 
taneously. Why  should  chance  create  species  endowed 
with  hereditary  properties?  Why  should  it  create 
certain  organisms  and  not  others? 

The  knowledge  of  fermentations  which  Pasteur  had  just 
acquired  forced  him,  therefore,  to  deny  the  hypothesis  of 
spontaneous  generations.  He  observed,  furthermore, 
that  after  having  abandoned  all  pretense  of  explaining 
the  origin  of  animals  visible  to  the  naked  eye,  and  thus 
accessible  to  experiment,  this  hypothesis  had  limited  its 
domain  to  the  realm  of  microscopic  organisms  whose 
minuteness  precluded  all  exact  scientific  research.  But 
in  this  quarter  he  had  had  some  experience  and  could 
hope  to  escape  some  of  the  difficulties  which  his  predeces- 
sors had  encountered.  In  spite  of  the  advice  of  M. 
Dumas,  he,  therefore,  approached  this  subject  with 
confidence. 

II 

BUFFON,   NEEDHAM,   SPALLANZANI,   SCHULTZE, 
SCHWANN,  SCHROEDER  AND  DUSCH 

Like  the  question  of  fermentations,  the  question  of 
spontaneous  generations  had  for  long  years  been  the 
subject  of  philosophical  speculations  and  oratorical 
dissertations.  Buffon  had  treated  it  with  solemnity. 
How  remain  indifferent  in  the  presence  of  the  very 


88  pasteur:  the  history  of  a  mind 

sources  of  life,  before  this  phenomenon  which  endows 
with  a  new  existence  the  organic  atoms  which  death  has 
just  dissociated  and  liberated?  There  is  no  death,  said 
the  believers  in  this  doctrine.  When  an  animal  dies, 
the  life  of  the  whole  vanishes  but  not  the  life  of  the 
elements,  not  that  of  its  ultimate  molecules.  Scarcely 
are  they  set  at  liberty  by  death,  than  they  at  once  begin 
an  independent  life,  become  isolated,  and  then  give  birth 
to  vibrios,  to  monads,  or  else  they  join  already  formed 
aggregations  which  attract  them,  and  thus  produce  the 
large  Infusoria.  "  Therefore,"  said  Buffon,  "it  is  in- 
evitable that  one  should  encounter  all  imaginable  grada- 
tions in  this  chain  of  organisms  which  descends  from 
the  most  completely  organized  animal  to  the  simple 
organic  molecule." 

We  see  the  connection  between  these  ideas  and  those 
which  during  the  same  epoch  explained  the  mystery  of 
fermentations.  It  was  the  same  organic  molecules, 
dissociated  by  putrefaction,  which  provoked  the  decom- 
position of  fermentable  substances  by  communicating 
to  them  their  own  movement,  and  which,  on  the  other 
hand,  became  organized  into  living  animalculse.  Sin- 
gularly, this  idea  of  a  common  origin  did  not  prevent  the 
fermentation  of  a  liquor  from  being  considered  as  some- 
thing quite  independent  of  the  Infusoria  which  might 
appear  therein,  and  these  two  kinds  of  evolution  of  the 
organic  molecule  were  even  regarded  as  opposed  to  each 
other,  and  the  Infusoria  as  harmful  to  the  fermentation 
which  was  called  the  principal  phenomenon. 

What  a  strange  way  of  looking  at  things  !  we  might  say 
to-day.  Why  turn  the  carpet  over  in  order  to  see  the 
design?  When  we  know  a  little  of  the  history  of  science, 
we  are  no  longer  astonished  at  this  kind  of  blindness. 
Our  conceptions  of  things  are  generally  more  compli- 
cated than  the  things  themselves.     It  is  rare  that  the 


BUFFON,    NEEDHAM,    SPALLANZANI,    ETC.  89 

human  mind  sees  simply:  it  is  experiment  alone  which 
leads  it  to  simplification  by  ways  which  are  sometimes 
very  tortuous.  But  to  attain  that  end  it  is  necessary 
that  the  mind  allow  itself  to  be  guided,  and  that  it  forget 
its  conceptions  and  its  formulas.  Nature  is  kindly;  it 
is  we  who  picture  her  as  bristling  and  sulky! 

In  the  domain  of  spontaneous  generations,  experiment 
had  been  introduced  for  the  first  time  in  1748  by  an  Irish 
Catholic  priest,  Needham,  whose  active  faith  did  not 
prevent  him  from  believing  in  an  actual  creation,  that  of 
the  animalculse  of  infusions.  In  order  to  prove  this,  he 
had  employed  a  mode  of  investigation  destined  to  play 
a  great  rôle  in  the  controversies  on  the  question.  He  had 
enclosed  some  putrefiable  substances  in  well-corked  flasks 
which  he  had  then  heated  by  plunging  them  into  hot 
ashes.  The  heat,  he  said,  must  kill  all  the  living  germs, 
visible  and  invisible,  which  may  be  introduced  into  the 
flasks,  for  none  are  known  which  resist  boiling  water. 
Now,  as  my  closed  flasks  withdrawn  from  the  ashes  be- 
come clouded  in  a  few  days,  and  are  peopled  with  micro- 
scopic organisms,  I  am  assisting  at  a  phenomenon  of 
creation  at  the  expense  of  dead  matter,  that  is  at  a 
spontaneous  generation. 

These  experiments,  accepted  for  a  long  time  without 
question,  met  in  1765  a  redoubtable  critic  in  another  abbé, 
the  illustrious  Spallanzani,  who,  by  repeating  the  same 
experiments,  with  only  the  precaution  of  heating  the 
closed  flasks  longer  than  Needham  had  done,  suppressed 
all  production  of  Infusoria.  Therefore,  he  concluded, 
Needham  did  not  heat  enough,  and  as  it  was  for  him  to 
prove  his  theory,  which,  besides,  is  in  disagreement  with 
the  facts  of  science,  it  vanished  of  its  own  accord,  the 
only  fact  on  which  it  could  rest  having  been  shown  to  be 
inexact. 

Not  at  all,  replied  Needham,   although  with  much 


90  pasteur:  the  history  of  a  mind 

courtesy.  If  your  infusions  remain  sterile  it  is  because 
you  heat  too  much.  You  alter  thus  the  air  in  the  flasks, 
or  else  you  destroy  the  vegetative  force  of  your  liquids. 
The  first  of  these  objections  was  acceptable,  although  it 
lacked  force  and  precision  in  an  epoch  when  the  composi- 
tion of  the  air  was  still  unknown.  But  what  was  to  be 
said  of  the  second?  The  vegetative  force  of  the  liquid, 
does  not  that  recall  invincibly  the  dormative  property  of 
opium,  ridiculed  a  hundred  years  before  by  Molière? 
This  strange  conception,  nevertheless,  met  with  favor, 
and,  if  I  recall  it,  it  is  because  the  idea  served  as  a  banner. 
If,  in  the  discussions  on  spontaneous  generations,  there 
have  always  been  savants,  who,  like  Spallanzani,  have 
endeavored  never  to  go  beyond  experiment,  there  also 
have  been  always  those  who,  like  Needham,  have  not 
hesitated,  in  a  time  of  great  need,  to  have  recourse  to 
the  vegetative  force,  to  the  creative  power  of  infusions,  or  to 
other  conceptions  not  less  vague  and  chimerical.  There, 
as  everywhere,  has  been  the  tribe  of  those  who  love  to 
deceive  themselves  with  words. 

Be  that  as  it  may,  the  celebrated  debate  raised  be- 
tween Needham  and  Spallanzani  was  left  without  any 
definite  conclusion,  each  of  the  adversaries  showing 
clearly  that  the  other  was  wrong  on  some  points,  but  not 
proving  that  he  himself  was  right  on  all.  However, 
science  in  its  onward  march  validated  or  invalidated 
their  arguments.  We  have  said  that  Gay-Lussac,  by 
studying  the  conserves  of  Appert,  which  were  nothing 
more  than  the  application  to  domestic  economy  of  the 
results  of  Spallanzani,  found  that  the  air  in  the  tins  no 
longer  contained  oxygen:  this  seemed  to  justify  the  first 
objection  of  Needham  given  above.  But  in  1836,  it 
occurred  to  Schultze  to  replace  with  ordinary  air  the  air 
in  the  flasks  of  Spallanzani.  After  having  determined 
that  they  are  sterile,  he  shows  that  they  remain  sterile 


pouchet,  pasteur:  the  germs  of  the  air      91 

when  he  introduces  air  which  he  has  simply  made  to 
bubble  through  concentrated  sulphuric  acid.  One  of 
these  experiments  lasted  from  May  to  August,  but,  al- 
though this  air  was  incessantly  renewed,  it  never  caused 
any  production  of  Infusoria:  this  proved  that  Gay- 
Lussac  was  wrong,  and  Spallanzani  right. 

The  following  year  Schwann  obtained  the  same  result 
as  Schultze  by  using  air  heated  by  passage  through  a 
bath  of  fusible  alloy.  Later  (1854),  Schroeder  and 
Dusch  replaced  the  heated  air  by  air  simply  filtered 
through  cotton,  and  from  them  dates  the  introduction 
into  microbiology  of  cotton  plugs  for  filtering  air. 

Reading  to-day  of  their  experiments,  we  ask  ourselves 
why  they  did  not  bring  universal  conviction.  What 
did  they  signify  save  this:  that  there  was  in  the  air  a 
principle  of  life  which  sulphuric  acid,  heat,  filtration 
through  cotton,  destroyed?  This  principle  was,  there- 
fore, neither  a  gas  nor  a  vapor,  nor  one  of  those  solid 
bodies  which  heat  respects.  It  could  only  be  an  organic 
substance.  How  is  it  that  Schwann  and  Schultze  did 
not  as  resolutely  bring  the  partisans  of  spontaneous 
generation  face  to  face  with  this  dilemma,  as  Pasteur  was 
to  do  10  years  later:  this  organic  substance  which  heat 
and  sulphuric  acid  destroy,  which  cotton  arrests,  can 
only  be  living  or  dead.  Why,  being  forced  to  choose,  do 
you  take  the  hypothesis  the  most  contradictory  to  that 
offered  by  the  best  known  branches  of  science? 


POUCHET,  PASTEUR:  THE  GERMS  OF  THE  AIR 

In  order  to  assume  this  tone  of  authority,  it  would 
have  been  necessary  to  confront  the  partisans  of  spon- 
taneous generation  with  some  experiments  which  were 


92  pasteur:  the  history  of  a  mind 

irreproachable  and  always  successful,  but  no  such  were 
available.  Experiments  which  had  been  the  most  con- 
vincing often  failed,  without  any  one  being  able  to  tell 
why.  Even  to-day,  when  our  technic  is  better,  we  can 
not  be  sure  of  obtaining  the  results  of  Spallanzani. 
Tyndall,  whose  experimental  skill  was  very  great,  has 
often  repeated  in  vain  the  experiments  of  Schultze.  In 
short,  there  were  certain  substances,  milk,  albumen, 
macerations  of  meat,  which  neither  nitration,  nor  heating 
of  the  air  preserved  from  alteration,  and  we  have  seen 
that  Helmholtz  admitted  for  these  substances  a  kind  of 
spontaneous  generation.  But  to  admit  it  in  one  case, 
was  to  admit  it  in  all.  Wherever  there  was  a  doubtful 
case,  one  flask  remaining  fertile  in  spite  of  the  precau- 
tions taken,  spontaneous  generation  had  the  right  to 
seize  upon  this  result,  and  to  say  "  It  is  I  who  have  pro- 
duced this.  Life  is  a  fragile  thing  to  preserve;  more 
fragile  still  to  produce.  It  is  all  to  no  purpose  that  you 
train  your  fingers  to  manipulate  it  delicately;  you  thwart 
it  without  knowing  it,  and  it  is  sometimes  just  because 
you  are  unskilful  that  you  see  it  appear." 

And  these  were  not  the  only  reasons.  The  partisans 
of  spontaneous  generation  had  the  best  of  it  in  the  dis- 
cussion, and  they  could  say:  "We  who  do  not  know  on 
what  life  depends  and  who  make  it  arise  from  nothing, 
we  are  exempt  from  the  obligation  of  showing  you  its 
origin  and  causes.  But  you  who  attribute  it  to  pre- 
existing germs,  show  us  then  these  germs!  Above  all, 
show  them  to  us  in  sufficient  number  and  variety  so 
that  each  bubble  of  air  can  people  with  numerous  and 
varied  organisms  the  various  infusions  which  we  may 
ask  it  to  fecundate.  For,  finally,  specificity  is  one  of  the 
consequences  of  your  way  of  looking  at  things.  But  we 
have  not  forgotten  a  certain  experiment  of  Gay-Lussac 
in  which  some  grape  juice,  sterile  at  first,  was  made  to 


pouchet,  pasteur:  the  germs  of  the  air      93 

ferment  upon  the  entrance  of  some  bubbles  of  air.  You 
say  these  bubbles  brought  with  them  some  germs  of 
yeast,  but  they  brought  something  else  into  an  infusion 
of  hay,  and  still  other  germs  into  a  meat  infusion,  etc. 
That  makes  a  great  many  germs!"  And  Pouchet,  who 
was  a  man  of  imagination,  added:  "The  air  thus  peopled 
would  have  the  density  of  iron." 

To  all  these  reasons  for  doubt,  add  this  one,  to  which 
we  have  referred  above,  and  which  was  more  profound 
and  more  powerful,  being  more  general,  namely  that,  in 
the  phenomena  of  spontaneous  generation,  even  more 
than  in  fermentations,  chance  seemed  to  be  master  and 
to  dictate  according  to  its  caprice  the  kinds  of  population 
of  the  infusions,  and  of  destruction  of  their  elements. 
Spontaneous  fermentations,  spontaneous  generations, 
chance,  all  these  words  harmonized  well  and  entered 
en  bloc  the  minds  of  the  scientific  men. 

It  is  here  that  we  again  recur  to  Pasteur,  and  to  that 
quality  of  which  I  have  just  spoken — the  superiority  of 
his  equipment  for  entering  the  fray.  The  idea  of  speci- 
ficity, born  of  his  work  on  the  fermentations,  involved 
that  of  hereditary  characters,  which  in  its  turn  led  to  that 
of  an  ordinary  kind  of  generation.  Pasteur  inclined, 
therefore,  logically  toward  the  theory  of  germs.  It  was 
only  a  question  of  proving  it  by  experimentation,  and  for 
that  he  was  better  equipped  than  any  scientific  man  of 
his  time.  He  was  familiar  with  the  infinitely  small 
organisms;  he  knew  how  to  manipulate  them.  He  had 
a  clear  field:  and  he  advanced  with  great  strides. 

"You  pretend,"  he  said  to  the  partisans  of  spontaneous 
generation,  "that  there  are  not  enough  living  germs  in 
the  air  to  explain  the  fertility  of  the  infusions  with  which 
this  air  comes  in  contact:  what  do  you  know  about  it? 
You  have  examined  the  dust  deposited  on  furniture  and 
on  stones;  you  have  gone  to  investigate  it  in  the  aban- 


94  pasteur:  the  history  of  a  mind 

doned  towers  of  old  cathedrals,  and  at  the  bottom  of  the 
hypogea  in  ancient  Egypt.  Futile  pains!  It  is  not  the 
dust  which  falls  and  is  deposited  that  interests  us  !  You 
will  find  therein  only  the  heaviest  parts  of  what  the  wind 
carries,  mineral  particles,  grains  of  starch  or  of  pollen, 
the  spores  of  cryptogams  or  even  bits  of  down,  of  cotton, 
of  wool  from  the  living  sheep  or  from  our  garments.  It 
is  not  these  particles  which  we  must  study,  but  rather 
those  which  we  see  dancing  without  repose  in  a  ray  of 
sunlight,  and  which  the  air  contains  in  the  state  of  a 
permanent  suspension." 

"  Furthermore,  your  study  of  the  dust  of  cathedrals 
gives  you  no  indication  of  quantity.     What  is  the  volume 

'-'*£&&'    ■    ®?*-M  -••.SSfcK.  ■:■  ^J:>v^;^r.i>iV^-,:;y.-'3 

*/■-■■!&■"*:■.:.  ■<.-: -a.-.. msi&ftfSn?- :■•:•':■  ■*..■;■    ©  !?.:•:- -.■:Z-~-9'À-  ■•l^if 

Fig.    9. — Dust   of   the   air   caught   by   aspiration   in   the   meshes  of   gun- 
cotton. 

of  air  which  has  deposited  the  little  mass  which  you  have 
studied,  and  subjected  to  microscopic  examination? 
You  do  not  know,  and  consequently  your  experiments 
may  well  open  the  question,  but  they  do  nothing  to  solve 
it." 

" Nevertheless  how  easy  the  thing  is!  Let  us  take 
the  cotton  filter  of  Schroeder  and  Dusch,  and  replace 
it  only  by  gun-cotton,  and  when  by  it  we  have  arrested 
in  its  passage  the  dust  in  a  determined  volume  of  air, 
let  us  throw  the  gun-cotton  into  a  mixture  of  alcohol  and 
ether  in  which  it  is  soluble.  All  the  weft  of  the  filter 
is  dissolved.  The  particles  of  dust  which  have  been 
caught  in  the  meshes  are  set  at  liberty  and  fall  to  the 


IN   THE   AIR   THERE   ARE    LIVING   GERMS  95 

bottom  of  the  liquid  if  one  leaves  it  in  repose.  We  may 
then  decant  the  liquid  above  them,  wash  them,  reunite 
them  finally  in  a  little  volume  of  water  and  study  them. 
And  behold  what  we  have  !  Look  and  tell  me  if  there  are 
not  there  present  corpuscles,  spherical  globules  (Fig.  9), 
round  or  oval  bodies,  so  like  the  spores  of  cryptogams 
or  the  eggs  of  Infusoria  that  no  micrograph  could  dis- 
tinguish them.  As  for  their  number,  we  find  many 
thousands  in  a  little  plug  of  cotton  through  which  has 
been  passed  for  twenty-four  hours  a  moderate  current 
of  air,  and  as  we  count  only  the  largest  of  these  globules 
figured  here,  those  which  have  a  clearly  organized  aspect, 
while  we  leave  aside  the  smallest,  which  are  evidently 
the  most  numerous,  failing  to  distinguish  them  from 
amorphous  elements,  you  must  conclude  that  there  is 
constantly  present  in  the  air  in  a  floating  state  the 
means  of  life  for  all  the  infusions  which  you  put  in 
contact  with  it." 


IV 
IN  THE  AIR  THERE  ARE  LIVING  GERMS 

"But,"  you  will  say,  "what  assurance  have  you  that 
these  particles  of  dust  which  you  have  shown  us  are 
living,  or  at  least  that  they  contain  something  living? 
That  is  also  easy  to  prove.  We  take  the  flasks  of 
Spallanzani,  or  of  Schwann,  for,  mark  it,  I  do  not  in- 
troduce any  new  method  of  work,  I  am  content  with 
operating  well  where  others  operated  badly,  with  avoiding 
causes  of  error  which  rendered  the  experiments  of  my 
predecessors  uncertain  and  contradictory.  We  take 
then  a  flask  containing  a  vegetable  or  animal  infusion: 
draw  out  the  neck  of  it  in  a  flame,  then  boil  the  liquid 
in  order  to  destroy  by  heat  everything  living  that  it 


96 


pasteur:  the  history  of  a  mind 


contains  (Fig.  10).  We  remove  the  air  which  it  contains 
by  the  current  of  vapor  which  the  boiling  produces: 
we  shall  sterilize  at  the  same  time  all  the  interior  walls. 
On  leaving  the  neck  of  the  flask,  the  vapor  traverses 
a  platinum  tube  heated  to  redness  in  a  gas  furnace 
(F.,  Fig.  10),  and  then  escapes  into  the  air.  When  the 
boiling  has  lasted  some  minutes,  we  extinguish  the  flame 
under  the  flask;  the  liquid  cools;  the  vapor  condenses: 
it  is  replaced  by  air  which  will  have  traversed  the  red- 
hot  tube  of  platinum,  where  everything  organic  contained 
in  it  will  have  been  burned.  When  the  flask  is  cold, 
we  separate  it  from  the  rest  of  the  apparatus  by  fusing 


Fig.  10. — Method  of  heating  the  air  (to  free  it  from  germs)  before  intro- 
ducing it  into  flasks. 

its  taperiug  neck  in  a  blowpipe.  We  shall  have  there 
a  flask  of  Spallanzani,  that  is  to  say  an  organic  infusion 
in  contact  with  air  containing  all  its  oxygen,  but  robbed 
of  everything  living,  and  even  organic,  which  it  contained. 
Very  well,  nothing  will  be  produced  there;  the  infusion 
remains  clear  because  we  have  allowed  nothing  living  to 
enter  it. 

"Now,  for  this  is  not  the  end,  we  take  one  of  these  flasks 
which  has  remained  sterile,  and  by  a  simple  process, 
which  I  shall  not  stop  to  describe,  we  pass  into  its  neck, 
always  in  the  presence  of  air  sterilized  by  heat,  one  of 
these  little  pieces  of  cotton  soiled  by  the  dust  of  the  air, 
the  living  character  of  which  you  deny.     As  long  as 


IN   THE   AIR   THERE   ARE   LIVING   GERMS  97 

this  remains  in  the  neck  (Fig.  11),  the  liquid  of  the  flask 
retains  its  first  clarity.  At  the  end  of  15  days,  or  a 
month,  we  make  the  cotton  fall  into  the  infusion  by 
simply  inclining  the  flask,  and  we  shall  see  that  at  the  end 
of  24  hours,  the  liquid  will  become  clouded,  and  that 
after'48  hours  it  will  contain  millions  of  living  organisms. 
When  birth  is  given  there  to  cryptogamic  growths,  we 
shall  often  see  tufts  of  filaments  growing  out  around 
the  cotton  of  the  plug,  testifying  thus  to  their  affiliation 
with  the  germs  which  it  contained. 

"What  reply  will  you  make  to  this  experiment?     The 
microscope  has  shown  us  in  the  bit  of         /^^^v 
cotton   substances   of  an  amorphous        /  ^"^^ 

aspect  and  substances  with  an  organ-        Wgggpj' 

ized  aspect.     This  we  can  affirm  as  a    — W?îÊÊ 

result  of  our  first  experiment.     The      FlG.  n._ Flask  used 

Second,   which    I  have  jUSt   described,     by  Pasteur  in  his  study 

of    fermentations    and 

tells  us  that  among  the  substances  of  the  distribution  of 
on  the  cotton  there  are  some  that  are  JJ™*  in  the  atmos- 
living.  You  partisans  of  spontaneous 
generation,  you  are  condemned  to  seek  by  preference 
in  amorphous  and  dead  substances  the  enigma  of  the 
life  which  appears  in  the  infusions.  Behold  the  in- 
consequence into  which  my  experiments  drive  you, 
for,  mark  it,  they  are  no  longer  doubtful,  irregular, 
contingent  experiments,  but  they  succeed  100  times  in  a 
100,  provided  a  little  skill  is  used  in  performing  them. 
They  are  obedient  to  the  mind  as  though  following  to  the 
letter  the  excellent  program  drawn  up  by  the  Academy  of 
Sciences:  'They  are  freed  from  all  uncertainty  arising 
from  the  experiments  themselves.'  Repeat  them  with 
the  details  which  I  give  you  and  you  will  succeed  just 
as  I  have  done." 

One  can  divine  the  effect  of  an  argument  so  concise, 
and  having  the  charm  of^a  geometrical  demonstration. 


98  pasteur:  the  history  of  a  mind 

Pasteur  did  not  stop  midway.  "Do  you  pretend,"  he 
continued,  addressing  the  partisans  of  spontaneous 
generation,  "that  the  cotton,  as  such,  plays  some  part 
in  the  phenomenon?  Never  mind!  We  will  replace  it 
with  calcined  amianthus,  without  in  any  way  changing 
the  result.  You  pretend  that  the  cotton  would  have 
absorbed,  by  contact  with  the  air  which  has  traversed 
it,  some  vapor,  or  I  know  not  what  subtile  matter  which 
heat  can  destroy,  and  which,  entering  the  infusion  with 
the  cotton,  would  have  brought  there  one  of  the  condi- 
tions necessary  for  life.  Your  hypothesis  is  somewhat 
intangible.  But  there  is  nothing  more  mysterious  than 
life  itself,  and  I  will  reply  to  it. 

"After  having  introduced  into  the  flask  an  infusion 
capable  of  fermentation,  draw  out  the  neck  in  an  enamel- 
ler's  lamp,  in  such  a  way  as  to  make  a  bent  and  sinuous 
tube,  in  the  form  of  a  letter  S  (Fig.  12).  Then  boil  the 
liquid.  When  vapor  has  issued  from  the  orifice  of  the 
neck  for  some  minutes,  drawing  out  all  the  air  of  the 
flask  with  it,  extinguish  the  flame  and  let  the  flask  cool. 
The  flask  becomes  filled  with  ordinary  air  which  will  not 
have  been  heated,  and  which  will  enter  it  with  all  its 
elements,  both  known  and  unknown.  As  the  neck 
remains  open,  diffusion  will  produce  incessant  exchanges 
between  the  air  of  the  flask  and  the  atmosphere  outside. 
Nevertheless,  the  flask  remains  indefinitely  sterile.  How 
do  you  explain  this  result,  you  partisans  of  spontaneous 
generation?  There  you  have  organic  matter,  water,  air 
incessantly  renewed,  and  heat,  nevertheless  nothing 
appears  in  the  liquid.  You  will  say  that  the  genetic 
power  of  the  infusion  has  been  altered  by  the  boiling  to 
which  we  have  subjected  it.  But  if,  without  touching 
the  infusion,  I  cut  off  the  neck  of  the  flask  which  contains 
it,  in  such  a  way  as  to  leave  it  exposed  to  the  fall  of 
atmospheric  dust,  it  becomes  clouded  in  two  or  three 


IN   THE   AIR   THERE   ARE    LIVING    GERMS 


99 


days.  Did  the  genetic  power  then  wait  for  the  disappear- 
ance of  this  swan's  neck  in  order  to  manifest  itself? 
What  is  your  explanation  worth  in  the  presence  of  this: 
the  curves  of  the  neck,  remaining  moist  at  the  moment 
when  the  fire  was  extinguished,  washed  in  its  passage  the 
air  which  traversed  them  in  a  thin  thread?  In  the 
beginning  when  the  entrance  of  the  air  was  rapid,  the 
purifying  action  of  this  washing  was  doubled  by  that  of 


Fio.  12. 


-Swan-neck  flask  used  by  Pasteur  in  his  study  of  spontaneous 
generation. 


the  liquid,  still  hot  and  able  to  destroy  the  germs  which 
came  in  contact  with  it.  Later,  the  wet  walls  of  the 
neck  have  held  fast  the  germs  of  the  air  as  they  have 
passed  through  the  narrow  opening.  The  proof  of  this 
is  that  if  you  shake  the  flask  in  such  a  way  as  to  introduce 
into  the  curve  of  the  neck  a  little  drop  of  the  infusion, 
having  previously  closed  the  open  end  so  that  nothing 
new  will  enter,  this  drop  becomes  clouded,  and  if  you 
then  mix  this  drop  with  the  rest  of  the  liquid,  the  latter 


100  pasteur:  the  history  of  a  mind 

becomes  populated  just  as  if  the  neck  had  been  broken 
off.  Another  proof  is  this:  when  the  neck  is  removed 
one  often  sees  (Fig.  12)  the  first  development  of  growth 
directly  under  the  opening,  where  the  germs  from  the  air 
have  fallen  in." 


V 

RESPONSE    TO    THE    ARGUMENTS    IN    FAVOR   OF 
SPONTANEOUS  GENERATIONS 

"I  am  not  content,"  Pasteur  might  have  continued, 
condensing  his  powerful  argument,  "I  am  not  content 
with  giving  you  convincing  experiments  which  always 
succeed.  I  do  more  than  that.  I  explain  why  my 
predecessors  have  so  often  obtained  those  contradictory 
results  which  have  troubled  them  and  stayed  their 
decisions.  Thus,  always,  Schwann  and  the  others  have 
seen  their  best-contrived  experiments  fail  when  they 
placed  their  liquids,  if  only  for  an  instant,  in  contact 
with  mercury.  What  imprudence  !  Is  not  the  mercury 
constantly  and  necessarily  full  of  impurities?  Those 
particles  of  dust  which  come  to  it  from  the  air,  and 
which  collect  on  its  surface,  mingle  with  it  and  are 
carried  along  with  it  everywhere.  It  is  for  this  reason 
that  I  have  carefully  excluded  it  from  all  the  preceding 
experiments,  which,  performed  with  its  aid,  might  have 
been  easier  to  carry  out,  but  which  might  have  left  us 
uncertain  as  to  the  results. 

"And  then,  to  disturb  our  convictions,  there  is  also  the 
history  of  this  milk  which  curdles  or  putrefies  under 
conditions  where  beef  bouillon,  the  must  of  beer,  and 
other  infusions  remain  unaltered.  There  is  this  yolk  of 
egg,  or  this  meat  without  water,  which  we  cannot  pre- 
serve by  heating  to  100°  C.  and  keeping  afterwards  in 


DISTRIBUTION   OF   GERMS   IN   THE   AIR  101 

air  which  has  been  heated  or  filtered  through  cotton. 
There  are  those  exceptions  which  haunted  the  mind  of 
Helmholtz,  of  Schroeder  and  Dusch,  and  made  them 
admit  that  there  were  some  'decompositions  of  organic 
matter  which  needed  only  the  presence  of  oxygen  to 
start  them,'  that  is  to  say  that  spontaneous  generation 
was  alone  capable  of  explaining.  Very  well,  there  again 
spontaneous  generation  has  nothing  to  do  with  it. 
Only  carry  up  to  110°  C.  your  milk,  your  yolk  of  egg, 
your  meat,  and  you  will  preserve  them  intact  as  easily 
as  the  bouillon.  The  milk  needs  to  be  heated  a  little 
more,  and  that  is  all  there  is  to  it.  It  is  not  that  it 
contains  more  resistant  germs,  but  that  it  is  slightly 
alkalin,  and  in  an  alkalin  medium  germs  are  more  resist- 
ant to  the  action  of  heat.  The  proof  is  that  a  decoction 
of  yeast,  which  is  easily  sterilized  by  a  short  boiling  at 
100°  C.  when  it  is  slightly  acid,  needs  to  be  heated  to 
105°  C.  or  110°  C.  when  there  is  added  to  it  a  small 
amount  of  carbonate  of  lime.  It  behaves  then  like  the 
milk." 

We  shall  see  later  that  there  is  in  the  interpretation  of 
this  experiment  an  error  brought  to  light  by  Bastian, 
but  which  did  not  invalidate  the  conclusion,  for  Pasteur, 
when  he  was  deceived,  had  the  art  of  never  being  deceived 
more  than  half  way.  He  approached  the  mark,  when  he 
did  not  hit  the  bull's-eye.  We  shall  find  a  new  example  of 
this  in  the  complementary  demonstration  which  follows. 


VI 
DISTRIBUTION  OF  GERMS  IN  THE  AIR 

There  was  in  favor  of  spontaneous  generation  one  last 
argument  to  which  Pasteur  had  not  yet  replied.  It  is 
the  experiment  to  which  we  have  referred,  in  which  Gay- 


102  pasteur:  the  history  of  a  mind 

Lussac  had  seen  some  inert  must  of  grape  begin  to  fer- 
ment as  soon  as  he  placed  it  in  contact  with  some  bubbles 
of  external  air.  Men  had  concluded  from  this,  with 
some  appearance  of  justice,  that  there  was  in  each  bubble 
of  air  something  capable  of  starting  all  the  fermentations 
or  putrefactions  which  could  take  place  in  the  most  varied 
liquids  in  contact  with  air.  This  was,  it  is  true,  a  little 
too  liberal  an  interpretation  given  to  an  experiment  which 
had  been  performed  only  twice  and  had  succeeded  only 
once.  But  if  it  accorded  well  with  the  hypothesis  of 
spontaneous  generation  which  saw  in  the  oxygen  the 
only  cause  of  the  appearance  of  life,  it  could  not  accom- 
modate itself  to  the  theory  of  germs.  It  seemed  difficult 
that  there  should  be  sufficient  in  each  bubble  of  air  to 
populate  the  most  varied  liquids  with  the  most  varied 
microbes. 

What  degree  of  credence  and  of  generality  could  be 
attributed  to  the  experiment  of  Gay-Lussac?  This  was 
what  no  one  knew,  and  what  Pasteur  was  obliged  to 
study.  It  is  this  part  of  his  work  which  has  attracted 
the  most  attention,  not  that  it  is  the  best:  all  of  it  is 
valuable;  but  this  is  the  most  easily  understood,  and  the 
experiments  in  it  are  as  simple  as  they  are  convincing. 
Pasteur  took  again  his  flasks  with  a  straight  neck  drawn 
out.  He  brought  to  a  boil  the  organic  infusion  which 
they  contained,  and  after  having  driven  out  all  the  air 
from  the  interior,  through  the  open  extremity  of  the  neck, 
he  closed  this  at  the  moment  when  the  steam  was  given 
off  by  melting  the  glass  in  the  flame  of  a  blowpipe.  The 
flask  is  thus  practically  empty  of  air  when  it  is  cooled. 

He  then  took  20  or  40  of  these  flasks  to  the  place  where 
he  wished  to  make  a  study  of  the  air,  and  broke  the  necks 
with  a  long  pair  of  pincers,  having  first  taken  the  precau- 
tion to  pass  the  necks  and  the  pincers  through  the  flame 
of  an  alcohol  lamp,  in  order  to  kill  all  the  germs  which 


DISTRIBUTION   OF   GERMS   IN   THE   AIR  103 

might  have  been  deposited  there.  Furthermore,  through- 
out the  operation  he  kept  the  flasks  as  high  as  possible 
above  his  head,  so  as  to  avoid  the  dust  from  his  clothing. 
When  the  necks  were  broken,  there  was  a  hissing  sound  : 
this  was  the  air  entering.  The  flasks  were  then  re- 
sealed  in  the  flame  of  a  lamp,  and  carried  back  to  the 
thermostat. 

In  some  cases,  the  air  which  entered  contained  viable 
germs,  and  the  infusion  became  populated  with  various 
organisms;  in  others,  the  air  contained  nothing,  and  the 
infusion  remained  sterile.  There  were  always  some  flasks 
which  remained  intact,  although  each  had  received  from 
200  to  300  cc.  of  external  air.  To  say  that  there  are 
germs  in  the  air  is  not,  therefore,  to  say  that  they  occur 
everywhere,  or  even  that  they  are  very  numerous:  it  is 
saying  that  there  are  some  here  and  none  there,  that  we 
find  more  in  a  low  and  humid  place,  favorable  to  crypto- 
gamic  vegetation;  that  we  find  fewer  in  air  which  is  in 
repose,  like  that  of  the  cellar  of  the  observatory;  that  they 
will  be  the  more  rare  the  farther  we  go  from  cultivated 
land,  and  the  higher  we  ascend  a  mountain;  that  there 
will  be  almost  none  in  the  midst  of  the  Swiss  glaciers 
where  no  vegetation  can  live.  Pasteur  opened  a  great 
number  of  flasks  in  the  air  of  these  various  places,  and 
he  always  found  that  some  of  them  remained  sterile,  and 
and  the  greater  the  known  purity  of  the  air  at  the  point 
studied,  the  greater  the  number  of  these. 

All  the  researches  made  since  have  confirmed  the  truth 
of  this  conclusion.  The  air  is  much  less  populated  with 
germs  than  has  been  supposed,  much  less,  even,  than 
Pasteur  thought.  To-day  men  carry  on  with  security, 
in  this  regard,  either  in  the  laboratories  or  in  surgical 
wards,  operations  which  they  would  not  have  dared  to 
undertake  in  1862,  haunted  as  they  were  by  the  idea  of 
those  germs  in  the  air,  to  which  Pasteur  had  just  called 


104  pasteur:  the  history  of  a  mind 

attention  so  forcibly.  Time  was  needed  to  recover  from 
this  dazzling  fact  and  to  observe  more  accurately.  We 
shall  see  Pasteur  himself  working  to  harmonize  things, 
and  to  make  that  fit  into  his  last  theory  of  the  air  which 
his  work  on  spontaneous  generation  had  put  into  the 
first.  Simultaneously,  surgical  science  developed.  After 
Lister  and  Jules  Guérin,  who  were  preoccupied  especially 
with  avoiding  atmospheric  contagion,  came  the  present 
day  surgery  which,  neglecting  the  air,  directs  its  attention 
and  precautions  especially  to  liquids  and  solids,  persons 
and  things,  and  thus  it  is  that  little  by  little  we  come 
into  possession  of  the  truth.  This  work  on  spontaneous 
generations  has  opened  horizons  whose  profundity  we 
do  not  yet  know. 


DISCUSSION  WITH  POUCHET 

We  must  not  suppose  that  this  demonstration,  as  ex- 
act as  it  was,  produced  universal  conviction  immediately. 
It  became,  on  the  contrary,  the  occasion,  or  rather  the 
pretext,  for  polemics  which  did  not  confine  themselves 
wholly  to  the  scientific  field,  and  from  which  neither 
religion  nor  politics  were  excluded.  The  doctrine  of 
Pasteur  contradicted  certain  philosophical  doctrines;  it 
spoke  to  the  same  purpose  as  the  Bible.  In  politics,  or 
rather  the  politics  of  the  time,  this  was  a  conservative 
doctrine;  no  one  has  ever  been  able  to  understand  why. 
Nothing  further  was  needed  to  stir  up  against  it  certain 
men  and  certain  journals.  On  the  other  hand,  scientific 
men,  even  the  greatest  of  them,  do  not  always  have  un- 
biased minds,  or  minds  fitted  to  comprehend  everything. 
In  short,  there  was  a  raising  of  bucklers,  of  which  the 
men  of  my  generation  have  not  lost  the  recollection. 


DISCUSSION   WITH   POUCHET  105 

Now  that  the  dust  of  combat  has  fallen,  it  is  curious  to 
pass  in  review  the  events  of  the  strife,  of  which,  further- 
more, Pasteur  bore  the  brunt.  We  shall  discover  a 
Pasteur  whom  we  have  not  yet  known;  a  vigorous  and 
sometimes  a  hot-headed  polemic,  a  cautious  polemic 
also,  who  profits  by  what  his  adversaries  teach  him. 

I  shall  pass  rapidly  over  the  long  discussion,  opened 
with  Pouchet  in  the  first  place,  then  with  Pouchet,  Joly 
and  Musset.  This  discussion  created  a  great  deal  of 
stir  in  its  time,  but  science  did  not  derive  from  it  any 
new  truth.  In  order  to  obtain  a  spark,  it  is  necessary 
to  have  the  friction  of  iron  against  flint;  here  there  was 
only  that  of  iron  on  punk.  Pouchet  was  a  conscientious, 
erudite  naturalist,  animated  by  a  desire  to  arrive  at  the 
truth,  but  impelled  by  the  nature  of  his  mind  outside 
the  only  paths  where  it  is  to  be  found.  He  portrays 
himself  exactly  in  the  second  line  of  the  preface  of  his 
Traité  de  V heterogenic,  published  in  1859.  "  When  by 
meditation,"  he  says,  "it  became  evident  to  me  that 
spontaneous  generation  was  another  one  of  the  means 
which  nature  employs  for  the  reproduction  of  her  crea- 
tures, I  applied  myself  to  discover  by  what  processes  one 
could  demonstrate  the  phenomena."  I  picture  to  my- 
self how  Pasteur,  as  well  as  Tyndall  later,  must  have 
read  these  lines  with  stupefaction.  Thus,  behold  a 
scientific  man  who  calls  on  experiment  to  prove  a  truth 
which  he  considers  in  advance  as  certain — what  shall  I 
say — as  evident,  although  he  has  reached  it  only  by 
meditation!  How  much  in  accord  here  are  this  extra- 
ordinary mind  and  extraordinary  language!  Tyndall 
has  remarked  that  it  would  have  required  a  very  powerful 
bridle  to  hold  in  check  a  mind  so  strongly  biased.  Now, 
not  only  was  Pouchet  incapable  of  profiting  by  the  results 
of  a  well-performed  experiment,  but  he  was  a  very  medi- 
ocre experimenter  whenever  he  left  the  domain  of  natural 


106  pasteur:  the  history  of  a  mind 

history  and  entered  a  laboratory.  We  are  nonplussed 
before  some  of  his  pieces  of  apparatus.  Thus,  for  ex- 
ample, he  did  not  hesitate  an  instant  to  send  a  current 
of  water  vapor  through  a  drying  tube  containing  pumice 
stone  saturated  with  sulphuric  acid.  But  aside  from 
these  defects  as  a  scientific  man,  he  had,  as  vulgariser 
and  polemic,  some  remarkable  qualities — a  wide  knowl- 
edge, a  boldness  of  affirmation  which  betokened  a  sin- 
cere conviction,  and  a  ready  pen  which  wrote  without 
growing  weary. 

In  comparison  with  Pouchet,  Joly,  professor  of  zoology 
of  the  Faculty  of  Sciences  of  Toulouse,  and  Musset, 
head  of  an  institution  in  the  same  city,  were  some- 
what lost  to  sight.  Lesser  metaphysicians  than  Pouchet, 
they  seemed  quite  as  incapable  of  knowing  what  con- 
stituted a  well-performed  experiment.  It  was  Joly, 
for  example,  who,  in  order  to  prove  that  there  was 
nothing  living  in  the  scum  of  dust  on  the  surface  of  the 
mercury,  introduced  what  he  gathered  into  water  (into 
distilled  water,  he  said  gravely)  and  was  astonished 
to  see  nothing  appear  in  the  mixture,  even  when  the 
eye  was  " armed  with  the  best  microscope."1  How 
answer  such  experiments? 

In  the  laboratory,  we  had  great  sport  over  these 
details,  but  the  master  could  not  laugh.  He  would  have 
been  wise  to  repeat  philosophically:  "We  have  not  the 
same  sort  of  brain,"  but  he  was  indignant  to  see  the 
truth  unrecognized,  and  contested  by  such  arguments, 
and  to  encounter,  even  in  the  Academy  of  Sciences, 
confrères  who  hesitated  between  him  and  his  adversaries. 
He  forgot  that  science  is  not  univocal,  and  that  one 
may  have  a  very  good  mind  and  still  comprehend 
nothing  of  a  mathematical  demonstration,   or  of  the 

1  Examen  critique  du  mémoire  de  M.  Pasteur  (Acad,  des  sciences  de 
Toulouse,  13  mai,  1863). 


DISCUSSION   WITH   POUCHET  107 

value  of  an  experimental  proof.  Fortunately,  on  his 
side  Pasteur  had  Balard  and  Dumas,  those  confrères 
whom  he  still  called  his  masters,  although  he  had  already- 
gained  the  leadership  himself. 

Balard  loved  science.  He  had  made  very  good  early 
progress  in  it,  and  his  discovery  of  bromine,  made  in 
his  pharmacy  laboratory  at  Montpellier,  had  placed  him 
above  his  peers.  It  sufficed  to  see  him  in  a  laboratory 
managing  a  piece  of  apparatus,  or  making  a  reaction, 
to  know  that  he  was  a  chemist  to  his  finger-tips.  But 
he  had  a  certain  natural  indolence,  and  he  was  thence- 
forth satisfied  with  his  share  of  glory.  To  the  scientific 
work  which  he  would  have  been  able  to  carry  on,  he 
preferred  that  which  he  found  done  in  the  laboratories 
he  frequented.  Although  each  day  having  the  intention 
of  returning  to  his  own  laboratory,  the  next  day  early 
he  yielded  to  the  desire  to  see  what  was  going  on  in  the 
laboratories  of  his  friends.  There  he  wished  to  see 
everything,  to  know  all  the  details,  and  we  told  him 
everything,  first,  because  he  had  an  open  mind  and  a 
generous  soul,  then,  because  it  would  have  been  difficult 
to  conceal  anything  from  him:  he  put  into  his  interro- 
gations at  the  same  time  so  much  shrewdness  and 
simplicity!  He  admired  with  all  his  heart  when  any  one 
showed  him  a  very  nice  demonstration!  And  then,  one 
was  sometimes  recompensed  for  this  confidence:  he 
would  suggest  an  idea  to  you,  and  reveal  to  you  a  method. 
It  was  he  who  conceived,  by  means  of  the  swan's-neck 
flasks  mentioned  in  the  preceding  chapter,  the  experi- 
ment designed  to  show  both  that  there  are  germs  ar- 
rested in  the  neck,  and,  by  introducing  into  the  neck  a 
drop  from  the  interior,  that  the  liquid  has  not  lost  its 
genetic  power.  We  see  the  drop  become  clouded  and 
populated,  while  the  liquid  in  the  flask  remains  unaltered. 
All  these  experiments  on  spontaneous  generation  trans- 


108  pasteur:  the  history  of  a  mind 

ported  Balard  with  delight  and  the  laboratory  became 
animated  with  his  expansive  joy  as  soon  as  he  entered. 

Dumas,  more  majestic,  and  at  this  time  a  power,  came 
more  rarely.  He  was  not  desirous  of  seeing  things  at 
such  close  range.  He  judged  them  from  his  superior 
height  and  was  no  less  a  very  good  judge;  consequently 
Pasteur  never  allowed  any  of  his  words  to  escape  him. 
It  was  a  little  in  spite  of  his  advice  that  Pasteur  had 
approached  this  question  of  spontaneous  generations, 
and  there  is  no  doubt  that  in  giving  this  advice  Dumas 
was  lacking  in  perspicacity,  so  much  was  this  study  in 
accord  with  the  mind  and  the  works  of  Pasteur.  But 
the  pupil  kept  his  master  in  touch  with  his  progress; 
and  he  was  never  more  happy  than  when  he  recounted  to 
the  laboratory  some  word  of  approbation  from  Dumas. 

Pasteur  had  need  of  these  encouragements,  for, 
decidedly,  he  could  not  make  up  his  mind  to  take  part 
in  the  little  war  which  the  partisans  of  spontaneous 
generation  were  pursuing  before  the  Academy  and  in  the 
journals.  But  this  internal  ebullition  did  not  prevent 
him  from  being  a  shrewd  manœuverer.  Consequently, 
he  allowed  the  most  hazardous  affirmations  to  be  made 
without  too  much  protestation,  contenting  himself 
with  exposing  from  time  to  time  the  weak  points  in  the 
experiments  which  were  opposed  to  his  own.  He  did 
not  wish  to  follow  his  adversaries  into  their  own  field, 
knowing  that  this  was  dangerous,  and  that  thus  they 
could  draw  him  where  they  wished  :  he  waited  patiently 
to  see  them  approach  his  territory.  Thus  when  they 
affirmed,  on  the  day  following  some  experiments  made 
on  the  Maladetta,  that  "  wherever  they  collected  a 
litre  of  air,  as  soon  as  they  put  it  in  contact  with  a  liquid 
capable  of  fermentation,  enclosed  in  a  matrass  hermeti- 
cally sealed,  the  latter  invariably  became  filled  with 
living  germs,"   on  that   day,   Pasteur  made  haste  to 


DISCUSSION   WITH   POUCHET  109 

seize  this  affirmation  on  the  wing.  The  experiments  on 
the  Maladetta,  made  apparently  under  the  same  con- 
ditions as  his  own,  contradicted  them  absolutely.  He 
demanded  that  the  Academy  of  Sciences  name  a  com- 
mission before  which  each  of  the  adversaries  should  re- 
peat his  experiments,  that  commission  to  say  on  which 
side  was  the  truth. 

This  was  in  truth  a  curious  episode,  and  a  very  in- 
structive one,  as  we  shall  see.  Requested  to  repeat 
their  experiment  immediately,  MM.  Pouchet,  Joly  and 
Musset,  began  by  demanding  postponement  until  warm 
weather.  The  demand  was  singular:  the  heat  of  the 
thermostat  is  a  perfect  substitute  for  the  heat  of  the 
sun,  and  if  the  doctrine  of  spontaneous  generation  is 
true  in  July,  it  ought  to  be  true  in  December.  The 
commission  succeeded,  nevertheless,  in  bringing  before 
it  in  June  all  the  adversaries  in  question.  We  had 
come  from  the  laboratory  of  the  normal  school  with 
everything  that  was  needed  to  repeat  the  experiment 
in  dispute:  Pouchet,  Joly  and  Musset  had  come  alone 
and  unarmed.  It  was  soon  evident  that  they  had  no 
desire  to  fight.  Having  tried  various  dilatory  methods, 
but  being  brought  back  incessantly  to  the  question 
in  point  by  the  severe  tone  of  Dumas,  and  by  the  slightly 
mocking  pleasantry  of  Balard — they  ended  by  declar- 
ing that  they  made  default  and  retired. 

The  battle  was  won,  for  Pasteur  was  sure  of  his 
experiments  which  succeeded  once  more  in  the  hands  of 
the  <  ommission  as  an  incisive  report  by  M.  Balard, 
inserted  in  the  Comptes  rendus  de  l'Académie  des  Sciences, 
testified.  Had  any  one  told  us  then  that  this  brilliant 
victory  amounted  to  nothing  he  would  have  surprised  us 
very  much.  Nevertheless,  such  was  the  case.  Pasteur 
was  right;  but  Pouchet,  Joly  and  Musset,  were  right 
also,  and  if,  instead  of  withdrawing,  they  had  repeated 


110  pasteur:  the  history  of  a  mind 

their  experiments,  they  would  have  embarrassed  the 
Commission  very  much,  and  Pasteur  would  not 
then  have  known  how  to  reply  to  them. 

It  is  in  reality  quite  true  that  if  one  opens,  at  any 
point  whatsoever  on  the  globe,  flasks  filled  with  a 
decoction  of  hay,  as  Pouchet,  Joly  and  Musset  did, 
it  often  happens  that  all  the  flasks  become  clouded 
and  filled  with  living  organisms.  In  other  words,  with 
this  infusion  the  experiments  of  Pasteur  with  the 
water  of  yeast  do  not  succeed,  and  one  is  led  to  admit 
that  the  air  which  enters  into  all  thé  flasks  carries 
germs  into  them. 

Let  us  say  immediately  that  the  germs  of  this  air 
are  a  negligible  quantity,  and  that  any  one  would 
obtain  the  same  result  by  filling  the  flasks  with  air 
sterilized  by  heat.  The  fact  is  that  the  germs  already 
exist  in  the  infusion.  They  have  resisted  boiling, 
as  is  the  case  with  a  great  number  of  micro-organisms. 
They  have  remained  inert  as  long  as  the  flask,  sealed 
during  the  boiling,  remains  devoid  of  air.  They 
develop  when  the  air  enters,  thanks  to  its  oxygen. 
But  Pasteur  did  not  yet  know  this  fact.  Pouchet, 
Musset  and  Joly  were  not  any  more  aware  of  it,  but 
if  they  were  ignorant  of  the  explanation,  they  had 
observed  the  fact,  and  if  they  had  been  better  experi- 
menters, more  men  of  the  laboratory,  if  they  had  studied 
more  thoroughly  the  conditions  of  their  success,  they 
would  have  accepted  the  challenge,  and  would  have 
won  the  battle,  or  at  least  each  of  the  adversaries  would 
have  retained  his  own  position. 

Perhaps  it  would  have  been  better  had  things  taken 
this  turn,  and  the  Academic  commission  been  obliged 
to  determine  that  all  of  the  adversaries  were  right, 
instead  of  putting  an  end  to  its  labors  by  a  bulletin 
announcing  the  victory  of  one  of  them.     Pasteur  would 


DISCUSSION   WITH   FRÉMY  111 

have  found  that  he  had  been  deceived  in  some  particu- 
lars, but  he  was  not  a  man  to  sulk  before  the  truth, 
and  some  ideas  which  did  not  enter  into  science  until 
ten  years  later,  would  have  found  their  place  there 
at  once  to  the  great  advantage  of  all.  We  were,  in 
reality,  obliged  to  wait  until  the  contest  with  Dr.  Bastian 
in  1876  to  rediscover  them.  But  the  episode  is  not  less 
curious,  when  we  consider  that  the  passing  error  of 
Pasteur  had  also  its  good  side  and  its  advantages.  This 
is  a  good  illustration  of  what  a  series  of  judgments, 
revised  without  ceasing,  goes  to  make  up  the  incon- 
testible  progress  of  science.  We  must  believe  in  this 
progress  but  we  must  never  accord  more  than  a  limited 
amount  of  confidence  to  the  forms  in  which  it  is  suc- 
cessively vested.  One  sometimes  reaches  the  truth  by 
error,  and  sometimes  error  by  the  truth. 


VIII 

DISCUSSION  WITH  FRÉMY 

Like  the  preceding,  the  discussion  which  opened  im- 
mediately between  Pasteur  and  Frémy  has  no  interest, 
even  when  studied  in  the  light  of  to-day.  I  venture  to 
say  that  it  never  had  any,  even  when  it  caused  heated 
discussions  in  the  séances  of  the  Academy  of  Sciences, 
it  was  so  incoherent  in  its  diverse  phases.  When  Frémy 
undertook  these  studies,  he  had  arrived  at  an  age  when 
the  mind  does  not  adapt  itself  easily  to  new  habits. 
He  had  never  been  good  at  unravelling  problems,  and 
this  one  demanded  much  ingenuity  and  penetration. 
He  had  never  been  familiar  with  the  microscope,  nor  with 
the  world  of  infinitely  small  organisms.  One  asks  then 
what  he  thought  to  accomplish  and  why  he  embarked 


112  pasteur:  the  history  of  a  mind 

on  this  galley.     Perhaps  he  wished  only  to  parade  there, 
for  she  manœuvered  in  full  sight  of  the  shore.     With 
all  his  qualities  as  a  man  and  a  savant,  Frémy  was,  in 
reality,  from  many  points  of  view  still  a  child.     Perhaps 
he  had,  notwithstanding,  the  intention  of  bringing  the 
ship  to  harbour,  but  what  an  illusion  regarding  his  quali- 
fications for  that  task  !    He  saw  indistinctly  and  reasoned 
awry.     In  order  to  explain,  for  example,  why  Pasteur's 
flasks  with  the  swan's  neck  did  not  become  clouded,  he 
conceived  the  idea  that  it  was  due  to  the  vitiation  of  the 
air,  resulting  from  the  absorption  of  the  oxygen  by  the 
liquid  in  the  flasks.     This  was  forgetting  the  experiments 
of  Schultze,  of  Schwann,  of  Schroeder,  even  those  of 
Pasteur.     But  this  also  was  nothing.     In  order  to  prove 
this  vitiation  of  the  air,  which,  according  to  him,  would 
prevent,  and  consequently  would  precede,  the  invasion 
of  the  microbes,  he  cited  some  air  analyses  made  on  flasks 
already  invaded,  and  where  the  aerobic  organisms  had 
naturally  absorbed  all  or  a  part  of  the  oxygen.     This  is 
unbelievable,  and  the  excellent  man  truly  did  not  merit, 
he  was  so  unsophisticated,  the  bit  of  harsh  treatment 
which  he  reaped  from  his  polemic.     Pasteur  did  not 
treat  him  as  a  serious  opponent.     He  was  amused  at 
seeing  him  rush  on  the  sword  of  his  adversary,  and  the 
tone  which  he  assumed  towards  him  is  well  illustrated 
by  the  following  phrase,  written  apropos  of  an  Academic 
discussion  in  which  Frémy,  made  angry  and  "  driven  to 
the  wall"  by  an  experiment  of  his  adversary,  had,  in 
order  to  explain  it,  and  relieve  his  own  embarrassment, 
conceived  the  idea  forthwith,   of  saying  that   "  small 
quantities  of  grape-must  do  not  ferment,"  and  that  there 
must  be  a  large  amount  of  it  for  fermentation  to  take 
place.     Thereupon,    Pasteur  parried:   "In    the    séance 
which  followed  that  in  which  M.  Frémy  made  this  decla- 
ration in  regard  to  small  quantities  which  do  not  ferment,  I 


DISCUSSION   WITH   FREMY  113 

gave  myself  the  malicious  pleasure  of  bringing  a  large 
number  of  very  small  closed  flasks,  into  each  of  which  I 
had  aspirated  a  drop  of  must  from  bits  of  crushed  grapes. 
I  broke  the  tapered  point  of  many  of  them  before  the 
Academy,  and  in  all  by  a  sharp  hissing,  which  was  heard 
at  a  distance,  the  fermentation  of  the  drop  of  liquid 
within  was  made  evident.  M.  Frémy  was  present  and 
kept  silent."1 

It  must  be  said  in  commendation  of  Frémy  that  he 
did  not  cherish  any  ill  will  because  of  these  thumps, 
feeling,  confusedly  at  first  but  more  and  more  clearly 
later,  that  his  opponent  was  right.  He  loved  the  truth, 
although  he  was  not  always  very  prompt  to  recognize  it, 
and  when  it  was  necessary  to  have  a  treatise  written  on 
the  ferments  and  fermentations  for  the  Encyclopedia, 
the  publication  of  which  he  directed  some  years  later,  he 
went  for  this  purpose  not  to  one  of  his  own  pupils,  but 
to  one  of  Pasteur's.2  No  one  could  terminate  a  polemic 
more  gallantly  ! 

This  discussion,  nevertheless,  did  not  remain  sterile. 
There  were  no  sterile  discussions  with  Pasteur,  because 
he  always  resorted  to  experiment  to  combat  the  argu- 
ments opposed  to  him.  He  thus  found  himself  drawn 
into  diverse  fields,  which  he  would  never  have  approached 
of  his  own  accord,  and,  as  he  had  perspicacity,  he  did  not 
fail  to  make  discoveries  therein.  Thus  it  is  that  he  de- 
rived from  his  controversy  with  Frémy  a  multitude  of 
curious  ideas  on  the  distribution  of  germs  in  the  air, 
and  germs  of  yeast  on  the  skins  of  the  grape — ideas 
which  he  utilized  much  later,  and  which  we  shall  en- 
counter again. 

1  Études  sur  le  vin,  p.  58. 

2  To  Emile  Duclaux,  author  of  this  book.  Frémy's  Encyclopédie 
Chimique,  Tome  ix,  lre  Section,  Chimie  Biologique  Par  M.  Duclaux. 
8  vo.,   p.  vii,  908.  Dunod,  Éditeur,  Paris,  1883.     Trs. 


114  pasteur:  the  history  of  a  mind 

IX 
DISCUSSION  WITH  BASTIAN 

The  only  discussion  which  produced  fruit  in  the  field 
in  which  it  arose  was  that  raised  by  Dr.  Bastian.  Like 
Frémy,  Bastian  had  taken  up  the  question  a  little 
thoughtlessly,  without  being  very  familiar  with  it,  and 
without  any  idea  of  its  difficulties.  His  first  experiments 
were  not  of  any  great  value;  but  he  had  tenacity,  fertility 
of  mind,  the  love  of  the  experimental  method,  if  not  an 
understanding  of  it,  and  he  has  given  us  ideas,  or  rather 
let  us  say  he  forced  Pasteur  to  gain  ideas,  the  absence 
of  which  had  hindered  the  progress  of  science.  All 
our  present  technique  has  arisen  from  the  objections 
made  by  Bastian  to  the  work  of  Pasteur  on  spontaneous 
generations.  It  was  Bastian  who  made  us  see  that  this 
work  which  had  been  so  vaunted,  abounded  in  false 
interpretations,  which,  he  said,  invalidated  its  con- 
clusions. It  was  Pasteur  and  his  pupils,  Joubert  and 
Chamberland,  who  showed  that  even  if  the  interpreta- 
tion had  sometimes  been  inexact  the  conclusions  were 
none  the  less  well  founded. 

Bastian's  first  attack  was  a  blow  straight  from  the 
shoulder.  "You  maintain,"  he  said,  "that  urine  boiled 
and  preserved  in  the  presence  of  superheated  air,  remains 
clear  and  sterile  because  you  have  allowed  no  germ 
to  penetrate  there.  I  say,  on  the  contrary,  that  the 
germs  have  nothing  to  do  with  it,  and  that  the  sterility 
of  the  liquid  is  due  only  to  the  fact  that,  in  spite  of 
all  your  care  and  your  dexterity,  you  have  not  known 
how  to  reunite  in  it  the  physical  and  chemical  conditions 
necessary  for  spontaneous  generation.  The  proof  of  it 
is  this  :  if  I  saturate  this  urine  with  a  little  potash  boiled 
and  freed  from  germs,  so  as  to  render  the  urine  neutral, 


DISCUSSION   WITH  BASTIAN  115 

or  a  little  alkalin,  and  if  I  put  it,  furthermore,  not  in 
one  of  your  ovens  where  it  is  not  sufficiently  hot,  but  at 
50°  C,  this  same  flask  of  urine  which  remains  sterile  in 
your  hands,  becomes  clouded  at  the  end  of  9  or  10  hours 
and  swarms  with  bacteria.  From  whence  can  they 
come,  if  not  from  a  spontaneous  generation?" 

Repeated  immediately  in  the  laboratory  of  Pasteur, 
the  experiment  was  successful.  It  is,  in  reality,  very 
exact,  but  what  must  we  conclude  from  it?  Pasteur 
could  not  interpret  it  as  Bastian  did.  He  acknowledged 
that  the  germs  were  there:  but  whence  did  they  come? 
In  this  investigation,  Pasteur  beat  about  the  bush  for  a 
long  time,  and  during  this  time  his  ideas,  like  his  discus- 
sion with  Bastian,  were  rather  confused.  I  will  simplify 
my  exposition  considerably  by  saying  that  these  germs 
for  which  Pasteur  demanded  an  explanation  from  ex- 
perimentation, could  be  derived  from  three  sources, 
unsuspected  up  to  that  time:  first  from  the  solution  of 
potash;  second  from  the  boiled  urine;  and  third  from  the 
walls  of  the  flask.  It  was,  we  see,  the  introduction  of 
solids  and  liquids,  as  conveyors  of  germs,  into  a  question 
where  up  to  that  time,  the  air,  chiefly,  had  been  incrimi- 
nated. Let  us  examine  separately  the  three  sources 
which  we  have  just  enumerated. 

The  solution  of  boiled  potash  may  contain  germs,  and 
yet  that  seems  surprising  when  one  thinks  that  this 
solution  is  made  with  a  piece  of  fused  potash  which,  in  a 
solid  state,  actively  attacks  animal  membranes  and 
destroys  everything  living.  Therefore,  it  is  not  this 
which  can  carry  the  germs,  and,  in  reality,  if  we  repeat 
the  experiment  of  Bastian,  replacing  the  solution  of  boiled 
potash  with  an  equivalent  fragment  of  fused  potash, 
the  experiment  does  not  succeed,  and  the  urine  con- 
tinues to  be  sterile.  Then  it  is  the  water  that  conveys 
the  germs,  and  in  studying  this  subject  Pasteur  and 


116  pasteur:  the  history  of  a  mind 

Joubert  were  in  reality  convinced  that  there  are  germs  in 
all  water,  even  in  that  which  has  been  carefully  distilled, 
when  it  is  collected  in  receptacles  which  have  been 
washed  with  water  containing  germs.  This  fact  had 
already  been  established  by  Burdon  Sanderson,  but  the 
French  savants  expanded  it  to  a  remarkable  degree,  and 
stated  it  more  precisely.  They  also  recognized  that 
only  the  waters  from  deep  sources,  those  which  had 
undergone  in  the  soil  a  slow  and  long  nitration  through 
capillary  spaces,  reached  the  surface  without  bringing 
back  the  germs  which  they  contained  in  abundance 
when  they  penetrated  the  soil.  They  were  filtered. 
We  find  there  all  the  ideas  which  have  been  so  useful  to 
us  later  on  the  subject  of  the  distribution  of  germs  in 
water,  and  out  of  which  was  evolved  for  purposes  of 
sterilization,  the  Chamberland  filter,  which  has  been  of 
such  great  hygienic  value. 

Nevertheless,  this  explanation  did  not  explain  every- 
thing, and  it  happened  sometimes  that  when  the  potash 
solution  had  been  thoroughly  sterilized,  or  even  replaced 
by  an  equivalent  fragment  of  potash  heated  to  redness, 
nevertheless  the  urine,  sterile  up  to  that  time,  became 
populated.  It  is  then  the  urine  which  supplies  the 
germs:  they  had  not  been  destroyed  by  the  boiling  to 
which  it  had  been  subjected,  and  thus  was  introduced 
into  science  this  very  fertile  idea  that  germs  could 
exist  in  a  living  state  in  a  nutrient  liquid  and  not  develop. 
Behold  the  contribution  of  Bastian!  Where  Pasteur 
saw  nothing  develop,  he  said:  " There  is  nothing;" 
Bastian  entered  the  field  and  said:  "Without  your  know- 
ing it,  there  is  something  of  which  you  prevent  the  evo- 
lution." Pasteur  retraced  his  steps  and  admitted: 
it  is  true  !  but  this  something  is  a  germ,  and  if  it  remains 
inert,  it  is  because  in  all  living  species  the  first  steps  in 
life  are  the  most  difficult  to  make. 


DISCUSSION   WITH  B  ASTI  AN  117 

At  this  time,  fortunately,  Pasteur  had  already  con- 
ceived the  idea  of  the  spore,  the  egg  of  the  Infusorian, 
which  demands  other  conditions  for  its  existence  than 
those  with  which  the  Infusorian  itself  is  content.  The 
conditions  of  this  revivification  are  in  general  limited, 
and  each  species  has  its  own.  Because  of  this  fact, 
and  because  sometimes  these  conditions  are  very  delicate, 
it  is  possible  occasionally  for  two  scientific  men  who  work 
on  the  same  species  to  find  that  they  are  in  disagree- 
ment, because  of  an  insignificant  difference  in  their 
method  of  work.  Because  of  the  fact  that  the  conditions 
vary  with  the  species,  it  it  clear  that  these  savants  will 
be  still  more  likely  to  contradict  each  other  if  they 
work,  as  is  almost  always  the  case,  on  different  species, 
and  behold  herein  a  hitherto  scarcely  dreamed-of  expla- 
nation of  a  multitude  of  contradictions  in  the  experi- 
mental study  of  spontaneous  generations. 

This  element  of  mystery,  now  revealed,  was  calculated 
to  arouse  zeal  in  the  laboratory  of  Pasteur.  It  was  soon 
recognized  there  that  two  conditions  govern  the  re- 
juvenescence of  the  germ,  the  reaction  of  the  liquid 
and  the  presence  of  air.  This  was  especially  the  work  of 
Chamberland.  In  a  liquid  which  is  too  acid,  germs 
heated  to  100°  C.  remain  alive,  but  inert.  Diminishing 
or  neutralizing  the  acidity  opens  the  field  for  them.  This 
is  what  Bastian  did,  and  his  experiment  contained 
nothing  contradictory  to  the  germ  theory.  It  is  true 
that,  by  way  of  retaliation,  he  ought  to  have  recognized 
the  existence  of  living  germs  in  the  flasks  which  Pasteur 
regarded  as  sterile,  and  from  which  he  deduced  evidence 
against  spontaneous  generation.  But  the  evidence  re- 
mained good,  although  the  witness  was  untrustworthy: 
heating  to  115°  or  120°  C.  the  liquids  which  Pasteur  had 
been  content  to  heat  to  the  boiling  point,  sufficed  to 
destroy  everything  that  was  living  therein,  and  to  give 


118  pasteur:  the  history  of  a  mind 

to  the  experiment  entire  security,  and  consequently 
all  its  significance.  The  practice  of  heating  to  120°  C. 
all  liquids  which  are  to  be  sterilized  dates  from  this  time. 
It  was  the  advent  of  the  autoclave  into  the  laboratory. 

Air  is  often  another  important  factor  in  the  revivifi- 
cation of  germs,  and  here  it  is  that  we  find  again  the 
experiment,  cited  above,  of  Pouchet,  Joly,  and  Musset. 
They  worked,  as  I  have  said,  with  a  hay  infusion, 
obtained  by  macerating  hay  in  tepid  or  hot  water,  which 
was  then  filtered  and  boiled.  But  this  hay  contains 
ordinarily,  as  Cohn  has  since  shown,  an  elongated 
bacillus  forming  a  pellicle  on  the  surface  of  the  infusion 
when  it  develops  in  it,  and  changing  into  very  resistant 
spores.  It  is  the  famous  Bacillus  subtilis  which  is 
everywhere  widespread,  and  owes  its  ubiquity  solely  to 
the  fact  that  it  is  admirably  equipped  for  the  strife, 
being  one  of  the  most  resistant  of  known  organisms.  Its 
spores,  particularly,  can  withstand  several  hours  of 
boiling  without  being  killed,  but  they  are  the  more 
difficult  to  rejuvenate  the  more  maltreated  they  are. 
If  we  seal,  in  a  flame,  the  neck  of  a  flask  which  contains 
them,  at  the  time  when  the  liquid  in  which  they  are 
submerged  is  boiling,  they  are  not  killed,  but  they 
do  not  develop  in  the  liquid  when  it  has  been  cooled  and 
put  in  a  thermostat,  because  air  is  lacking.  If  we  allow 
air  to  enter,  the  infusion  becomes  populated  and  this 
is  also  the  case  if  we  allow  only  heated  air  to  enter;  for 
the  air  does  not  act  by  introducing  germs,  as  Pasteur 
believed  at  the  time  of  the  debate  before  the  Academic 
commission  on  spontaneous  generations:  it  is  its  oxygen 
alone  which  comes  into  play. 

We  see  here  how  necessary  ingenuity  and  discernment 
are  in  these  matters.  Here  we  have  an  experiment 
in  which  air  coming  into  contact  with  an  infusion  brings 
to  it  fertility.     This  was  performed  by  Gay-Lussac  with 


DISCUSSION   WITH  BASTIAN  119 

the  must  of  grape,  by  Pouchet  with  hay-infusion,  by 
Bastian  with  urine.  Gay-Lussac  concludes:  it  is  the 
oxygen  which  has  vivified  the  dead  matter;  Pouchet  and 
Bastian  say:  it  is  spontaneous  generation.  Then  comes 
Pasteur,  who  first  said:  "Not  at  all;  it  is  germs."  Then, 
when  he  had  been  shown  that  he  was  deceived  :  "  It  is  the 
cooperation  of  the  germs  and  of  the  oxygen."  The  germs 
always  played  a  part,  and  in  that  respect  he  won  his  case. 

Finally,  these  germs,  so  resistant,  so  widespread, 
present  in  all  waters,  stick  to  the  walls  of  the  receptacles 
washed  with  these  waters,  by  a  mechanism  analogous 
to  that  which  fixes  them  in  the  capillary  tubes  of  a 
porcelain  filter.  There  they  dry,  and  once  dried,  they 
are  still  more  resistant.  The  heating  to  120°  C.  of  a  flask 
half  full  of  liquid  may  sterilize  only  the  moistened  part, 
allowing  life  to  persist  in  the  regions  which  are  not  in 
contact  with  the  liquid.  In  order  to  destroy  everything, 
it  is  necessary  to  subject  the  dry  walls  to  180°  C.  Hence 
the  utility  of  flaming  all  the  receptacles  used  in  micro- 
biology, and  behold  once  more  a  practice  arising  like 
the  autoclave,  from  the  laboratory  of  Pasteur,  and  which, 
along  with  it,  established  a  good  technique  and  made 
the  future  secure. 

Thus  it  was  that,  little  by  little,  knowledge  extended 
and  became  more  exact,  and  that  all  the  objections  to  the 
germ-theory  ended  in  giving  us  more  exact  ideas  on  the 
subject  of  the  evolution,  the  distribution,  and  the  char- 
acteristics of  germs.  From  this  point  of  view,  one 
may  say  that  all  these  discussions  have  been  useful 
because  they  have  given  rise  to  new  experiments.  The 
controversy  with  Bastian  was  the  most  useful  because 
there  the  two  adversaries  without  being  of  equal  force 
had  the  same  creed  and  the  same  faith.  Bastian 
rendered  a  service  to  science;  he  lashed  it  on  its  weak  side, 
but  he  compelled  it  to  advance. 


PASTEUR 

(Courtesy  of  Dr.  Winford  H.   Smith,   Superintendent,  Johns 
Hopkins  Hospital.) 


FOURTH  PART 
WINES  AND  [VINEGARS 


INDUSTRIAL  METHODS  IN  THE  MANUFACTURE  OF 

VINEGAR 

The  theory  of  Liebig  in  regard  to  fermentations, 
which  Pasteur  had  combatted,  was  applied  also  to  a 
category  of  phenomena  to  which  Liebig  had  given  the 
name  Eremacausis,  or  dry  rot,  and  which  were  especially 
phenomena  of  oxidation  in  contact  with  the  air.  The 
type  to  which  he  referred  them  by  preference  was  the 
oxidation  of  alcohol  by  platinum  black,  discovered  by 
Dôbereiner.  When  drops  of  concentrated  alcohol  are 
allowed  to  fall  on  finely  divided  platinum,  the  mass  be- 
comes hot  and  gives  off  vapors  which  have  both  the 
suffocating  odor  of  aldehyde,  and  the  penetrating  and 
pungent  odor  of  vinegar.  The  explanation  of  the  phe- 
nomenon is  very  simple.  The  alcohol  is  burned  at  the 
expense  of  oxygen  which  the  platinum  holds  condensed 
in  its  pores.  A  partial  oxidation  gives  aldehyde;  a  more 
complete  one,  acetic  acid;  an  oxidation  still  more  com- 
plete would  give  carbonic  acid,  as  when  alcohol  burns 
with  a  flame  in  contact  with  air.  As  for  the  platinum, 
it  remains  unaltered. 

Such  was  the  type,  purely  chemical,  to  which  Liebig 
referred  the  oxidizing  action  of  the  soil  on  the  organic 
substances  which  it  contains,  nitrification,  the  dry  rot 
of  wood,  the  oxidation  of  the  siccative  oils,  and,  by  ex- 

121 


122  pasteur:  the  history  of  a  mind 

tension,  the  different  processes  of  vinegar-making  by 
oxidation  of  the  alcohol  in  wine  or  fermented  liquors. 

Owing  to  his  study  of  the  different  processes  employed 
in  his  vicinity,  since  the  time  of  Schutzembach,  by  the 
vinegar  manufacturers  of  Germany,  he  had  some  right 
to  make  this  comparison.  In  a  pile  of  casks  with  the 
heads  knocked  in,  and  forming  a  hollow  column  several 
meters  in  height,  are  piled  loosely  shavings  of  beech, 
over  which  is  showered  a  feebly  alcoholic  liquid  to  which 
have  been  added  some  milligrams  of  acetic  acid  and  which 
contains,  furthermore,  a  little  acid  beer,  sharp  wine,  or 
some  other  organic  matter  in  process  of  alteration,  Deces- 
sary,  according  to  the  theory  of  Liebig,  to  act  as  a  fer- 
ment and  set  in  motion  the  phenomenon.  Under  these 
conditions  the  shavings  play  the  rôle  of  the  platinum 
black  and  do  it  more  economically.  On  coming  into 
contact  with  them  the  alcohol  oxidizes,  the  mass  be- 
comes heated,  and  the  pile  of  casks  forms  a  chimney  for 
a  current  of  air,  which,  entering  below,  diffuses  through- 
out the  mass,  bringing  constantly  to  all  points  new  oxy- 
gen, so  that  the  process  of  acetification  progresses 
rapidly.  As  with  platinum  black,  there  are  sometimes 
formed,  in  addition  to  the  acetic  acid,  suffocating  prod- 
ucts with  the  odor  of  aldehyde.  Finally,  to  complete 
the  resemblance,  the  shavings  seem  to  act  only  by  their 
presence.  After  10  or  20  years  of  use  in  the  manufacture 
of  vinegar,  they  are  intact,  being  as  sound  and  clean  as 
on  the  first  day. 

We  will  acknowledge  that  the  comparison  was  tempt- 
ing, and  will  understand  that  Liebig  could  not  resist  the 
temptation.  One  falls  easily  on  the  side  toward  which 
he  leans.  Pasteur  was  entitled  to  look  upon  the  question 
quite  differently.  In  connection  with  his  studies  on 
spontaneous  generation,  he  had  just  determined  that  all 
organic  substances  oxidize  very  slowly  in  contact  with 


METHODS   IN   THE   MANUFACTURE   OF  VINEGAK      123 

air  when  microbes  do  not  intervene;  but  the  acetifica- 
tion  in  the  German  process  is  very  rapid.  It  is  true 
that  it  was  not  immediately  plain  just  where  the  micro- 
organisms could  intervene  in  this  mass  of  shavings, 
which  always  remain  unchanged;  but  there  was  some- 
thing which  resembled  it  in  the  factory  of  Orléans,  a 
village  which,  for  a  long  time,  has  had  a  merited  reputa- 
tion for  its  vinegars. 

There  they  carry  on  operations  in  casks  lying  on  end 
in  piles  and  filled  about  two-thirds  full  of  a  mixture  of 
fermented  vinegar  and  unfermented  wine.  Now,  on  the 
surface  of  the  liquid,  in  the  casks  which  behave  properly, 
there  is  a  fragile  pellicle  which  the  vinegar-maker  takes 
great  pains  not  to  disturb  and  not  to  submerge,  because 
he  considers  it  a  precious  ally.  Experience  having 
taught  him  that  it  needs  air,  he  has  opened  for  it  a  large 
window  in  the  top  end  of  the  cask,  above  the  surface  of 
the  liquid.  He  watches  this  pellicle  and  cares  for  it. 
As  long  as  it  remains  spread  over  the  surface  of  the 
liquid,  all  goes  well;  if  it  is  broken  and  falls  in  fragments, 
all  is  lost.  It  is  then  necessary  to  produce  a  new  one; 
and  sometimes,  God  knows,  with  how  much  trouble, 
expense  and  groping  about!  A  blast  of  heat,  a  blast  of 
cold,  may  suddenly  interrupt  all  manufacture. 

What  then  is  this  pellicle  which  is  so  precious  and  so 
delicate?  Pasteur  had  been  asking  himself  this  question 
for  a  long  time,  but  he  only  felt  himself  ripe  for  the  study 
of  this  question  after  he  had  carried  out  his  studies  on 
the  nutrition  of  micro-organisms  and  on  the  spontaneous 
generations  which  we  have  reviewed.  He  was  hence- 
forth armed  and  equipped,  and  less  than  a  year  sufficed 
him  to  make  on  this  subject  one  of  those  researches  à  la 
Lavoisier,  which  immediately  become  classic  because  of 
their  fullness,  their  elegance  and  their  simplicity. 


124  pasteur:  the  history  op  a  mind 

II 
THE  MYCODERMA  OF  VINEGAR 

As  Pasteur  had  thought  it  out,  all  the  work  of  oxidation 
was  performed  by  a  micro-organism  differing  from  those 
with  which  he  had  been  familiar  up  to  this  time,  in  that 
it  is  an  agent  for  the  transmission  of  the  oxygen  of  the 
air  to  certain  substances.  These  functions  make  it 
necessary  for  it  to  live  in  contact  with  the  air  on  the  one 
hand,  and  with  the  nutrient  substance  on  the  other,  and 
it  develops  on  the  surface  of  the  liquid  in  the  form  of  a 
delicate  veil,  smooth  and  level  at  first,  later  in  folds, 
because,  when  the  organisms  become  too  crowded,  it  is 
necessary  for  them  to  pile  up  on  each  other.  This  form 
of  veil  won  for  this  organism  the  name  of  Mycoderma 
aceti,  or  the  mycoderma  of  vinegar. 

Three  things  were  remarkable  about  this  organism. 
In  the  first  place,  its  marked  aerobic  character.  It  was 
the  exact  antipode  of  the  butyric  vibrio,  previously  dis- 
covered, and  it  was  to  characterize  the  two  so  opposite 
functions  of  these  two  organisms  that  there  were  created 
with  the  collaboration  of  Chassang,  professor  of  Greek 
in  the  École  Normale,  the  two  words  aerobic  and  anae- 
robic. The  acetic  ferment  was  also  singularly  prolific. 
In  24  hours,  it  would  cover  the  surface  of  a  vat  of  any 
size  whatever,  with  a  fine  pellicle  of  cells  crowded  to- 
gether, provided  that  one  sowed  here  and  there  some 
cells,  as  seed.  These  form  islands  which  become  joined 
in  a  continuous  layer.  The  cells  of  the  ferment  are 
almost  twice  as  long  as  broad  (5,  Fig.  8).  It  takes  400 
of  them  placed  end  to  end,  or  800  placed  side  by  side,  to 
make  a  millimeter.  That  makes  a  minimum  of  30 
millions  of  cells  to  the  square  centimeter,  or  300  thou- 
sand millions  of  cells  in  a  vat  with  a  surface  of  a  square 


THE    MYCODERMA   OF  VINEGAR  125 

meter,  covered  in  24  hours.  The  ferment  best  known  up 
to  that  time,  the  yeast,  gave  figures  much  smaller  and  less 
striking. 

This  is  not  all,  for  we  are  about  to  see  appear  a  new 
conception,  which  the  future  will  make  productive — 
the  conception  of  the  fermenting  power.  These  300 
thousand  millions  of  cells  weigh  about  1  gram  and  can 
acidify  in  4  or  5  days,  when  the  conditions  are  favorable, 
10  kilograms  of  alcohol.  That  is  to  say,  each  one  of 
these  cells  demands  per  day  two  thousand  times  its  own 
weight  in  food  material.  And  here  there  is  raised  one 
of  the  corners  of  the  veil  which  for  so  long  a  time  has 
masked  from  us  the  grandeur  of  the  rôle  of  the  infinitely 
small  organisms.  Their  power  of  work  is  out  of  all  pro- 
portion to  their  weight.  With  a  feeble  volume,  they  can 
produce  great  effects:  we  understand  that  they  may 
occupy  a  great  place  in  the  economy  of  the  globe  and  yet 
pass  unperceived. 

The  oxidation  of  these  10  kilograms  of  alcohol  requires 
the  putting  into  play  of  more  than  6  kilograms  of  oxygen; 
that  is  to  say,  more  than  there  is  in  15  cubic  meters  of 
air.  We  explain  thus  the  utility  of  the  current  of  air 
ascending  in  the  column  of  shavings  in  the  German 
method,  and  of  the  large  open  window  in  the  upper  end 
of  the  Orléans  casks. 

This  oxygen,  which  it  derives  from  the  air  through  its 
aerial  surface,  the  mycoderma  transmits  to  the  alcohol 
through  its  submerged  surface.  But  oxidation  does  not 
always  take  place  in  the  same  way.  Sometimes  it  is 
arrested  in  the  aldehyde  state  and  the  organism  yields 
products  with  a  disagreeable  and  suffocating  odor.  As 
in  case  of  the  oxidation  due  to  platinum  black,  the 
process  is  arrested  half  way.  At  such  times  the  organ- 
ism lives  with  difficulty;  it  suffers.  Why  should  we  not 
say  that  it  is  sick?     Disease  and  death  are  the  natural 


126  pasteur:  the  history  of  a  mind 

attributes  of  life,  but  the  idea  of  disease  in  a  creature  so 
small,  was  none  the  less  original.  It  was  the  first  time 
that  it  had  presented  itself.  Since  then,  it  has  been 
greatly  developed. 

On  the  contrary,  sometimes  this  ferment,  instead  of 
being  arrested  half  way,  goes  beyond  the  acetic  acid 
stage,  exactly,  again,  like  the  platinum  black,  and  instead 
of  acetic  acid,  yields  water  and  carbonic  acid.  Then  it 
consumes  the  acetic  acid  which  it  has  formed,  and  here 
again  we  have  the  first  example  of  the  ability  of  a  living 
organism  under  certain  conditions  to  destroy  a  product 
which  under  other  conditions  it  has  manufactured.  The 
organism  consumes  the  acetic  acid  when  there  is  no  alco- 
hol at  its  disposal,  that  is  to  say,  it  consents,  when  it  is 
starving,  to  touch  a  food  which  it  scorns  and  rejects  in 
other  circumstances,  and  which  thus  has  accumulated 
in  the  ambient  liquid.  But  this  acetic  acid  is  its  second 
choice  of  food,  and  it  abandons  it  in  favor  of  alcohol  as 
soon  as  it  has  the  opportunity. 

Curious,  is  it  not,  this  choice  of  food  in  the  world  of 
infinitesimal  organisms!  What  prevents  us  from  seeing 
therein  an  act  of  volition  or  of  instinct?  Observe  that  it 
is  an  entirely  different  thing  from  finding  that  each  organ- 
ism has  its  own  food  material,  that  the  yeasts,  for  ex- 
ample, can  obtain  nourishment  only  from  sugar.  The 
acetic  ferment  can  make  a  choice,  and  show  preferences  : 
it  has  free  will.  I  know  well  that  it  is  governed  by  its 
needs,  but  how  many  acts  of  volition  have  as  a  cause, 
though  often  obscure,  only  that  of  satisfying  needs? 
Let  us  not  insist  upon  this  point,  however,  but  confine 
ourselves  to  noting  with  what  care  Pasteur  sought  by 
their  study,  as  soon  as  micro-organisms  had  brought 
him  into  contact  with  life,  new  light  on  the  physiology 
of  the  higher  organisms.  He  did  not  fail  to  compare  his 
acetic  ferment,  the  agent  of  oxidation,  with  the  red  cor- 


THE   MYCODERMA    OP  VINEGAR  127 

puscles  of  the  blood,  which  are  also  charged  with  trans- 
porting oxygen  to  the  tissues,  giving  it  up  to  certain  sub- 
stances in  preference  to  others,  thus  carrying  on  the 
oxidation  that  is  needed,  even  if  it  is  not  voluntary  and 
premeditated.  He  had  asked  himself  what  would  hap- 
pen if  the  red  corpuscles  should  become  diseased  in  the 
same  way  as  the  cells  of  the  acetic  ferment,  arrested  in 
their  development  in  the  aldehyde  stage  of  oxidation. 
In  short,  he  penetrated  through  his  micro-organisms,  into 
the  laws  of  physiology  and  pathology. 

The  practical  consequences  of  his  discoveries  equalled 
their  theoretical  promise.  They  restored  security  to 
the  Orléans  vinegar  manufacturers,  who  were  hence- 
forth masters  of  the  mycoderma  veil  in  their  casks 
instead  of  being  subject  to  its  demands  and  caprices; 
they  made  it  possible  for  the  boldest  of  these  men  to 
adopt  a  new  method  of  manufacture  whereby,  instead  of 
leaving  intact  for  a  long  period  the  pellicle  formed  on 
the  surface  of  the  liquid,  they  resowed  it  and  renewed 
it  at  frequent  intervals.  Thus  not  only  could  one  make 
more  rapid  progress,  but  could  regulate  the  production 
to  the  demand,  whereas,  by  the  old  Orléans  method 
production  must  be  going  on  constantly  and  the  casks 
could  not  lie  idle,  lest  they  should  become  inert. 

But  is  it  only  in  the  Orléans  process  that  the  microbe 
intervenes?  Not  at  all.  We  find  it  also  in  the  German 
process,  but  it  is  less  apparent  there,  because  it  is  formed 
in  much  less  quantity.  In  Orléans,  the  white  wines, 
rich  in  organic  matter,  are  used  especially  for  vinegar- 
making,  and  the  layer  which  develops  on  the  surface  of 
the  liquid  in  the  casks  forms  thereon  sometimes  a  thick 
veil.  In  Germany,  little  else  is  used  for  vinegar-making 
except  alcohols  diluted  with  water  and  mixed  with  that 
small  quantity  of  wine,  or  sour  beer,  which  Liebig 
demanded.     This  liquid  is  not  very  nourishing  and  seems 


128  pasteur:  the  history  of  a  mind 

unsuitable  as  food  for  even  the  least  exacting  micro- 
organism; but  it  is  sufficient,  and  if  one  scrapes  with  the 
point  of  a  knife  the  surface  of  these  beech  shavings,  which 
seem  so  sound  and  clean,  he  finds  there  a  transparent 
pellicle  formed  of  cells  entirely  similar  to  those  in  the 
Orléans  casks.  The  manufacture  of  vinegar  is  then 
everywhere  due  to  bacterial  action. 


Ill 
DISCUSSION  WITH  LIEBIG 

This  conclusion  was  not  calculated  to  please  Liebig, 
who  was  defeated  on  his  own  ground,  and  on  a  question 
where  the  close  analogy  between  the  industrial  results 
and  those  furnished  by  platinum  black  seemed  to  rule 
out  all  physiological  action.  An  old  champion  such 
as  he  could  not  yield  without  fighting,  and  he  retaliated 
with  two  memoirs,  the  one  On  fermentation  and  the  source 
of  muscular  energy,1  read  before  the  Royal  Academy  of 
Sciences  of  Munich  in  1868  and  1869,  the  other2  in- 
serted in  the  Proceedings  of  the  Bavarian  Academy  in 
1869.  Both  demonstrate  how  difficult  it  is  for  even 
the  most  eminent  scientific  man  to  adapt  himself  in  his 
old  age  to  new  ideas,  when  they  run  contrary  to  the 
current  of  those  in  which  he  has  passed  his  life.  Experi- 
ence and  erudition  are  then  a  restraint:  one  must  shed 
his  old  skin  and  abstract  himself  from  all  that  he  has 
learned. 

As  the  title  of  the  first  of  these  memoirs  indicates, 
Liebig  enlarged  the  scope  of  the  debate  and  returned 
to  the  question  of  alcoholic  fermentation  in  search  of 

1  Ann.  de  ch.  et  de  phys.,  t.  XXIII,  4e,  se.  p.  5. 
»  lb.,  p.  149. 


DISCUSSION   WITH   LIEBIG  129 

light  on  the  physiology  of  the  cell.  We  shall  not  follow 
the  discourse  in  all  its  developments,  which  are  some- 
times digressions,  but  shall  ask  only  what  it  had  to  reply 
to  the  new  doctrine  on  the  fermentations. 

On  this  point  his  position  became  more  and  more 
embarrassing.  Already,  at  the  time  when  he  had  first 
developed  his  theory,  he  had  been  obliged  to  admit  that 
the  yeast  was  a  living  organism  which  renewed  and 
destroyed  itself  continually,  and  it  was  only  the  products 
of  the  destruction  which  made  the  sugar  ferment.  That 
point  had  become  difficult  to  maintain  and  support 
after  Pasteur  had  shown  fermentation  to  be  a  cellular 
phenomenon.  It  is  curious  to  see  how  Liebig  extricates 
himself  from  this  difficulty.  He  considers  that  life  is 
accompanied  at  every  instant,  in  every  cell,  by  a  move- 
ment of  decomposition  and  reconstruction,  and,  naturally, 
it  is  to  the  first  that  he  has  recourse.  He  admits  then 
the  physiological  phenomenon  but  he  takes  into  con- 
sideration only  a  part  of  it  and,  once  more,  the  chemical 
side,  endeavoring  "to  reduce  the  chemical  decomposition 
of  the  sugar  to  a  simple  formula  common  to  all  analogous 
phenomena." 

The  attempt  is  bold,  and  we  recognize  in  it  the  general- 
izing mind  of  Liebig.  We  shall  see  how  he  succeeded. 
Let  us  note  in  the  beginning  that,  from  a  chemical  point 
of  view,  the  vital  phenomenon  of  Pasteur  does  not  differ 
essentially  from  the  phenomenon  of  movement  of  Liebig, 
and  that  it  is  possible  to  reconcile  them.  "I  admit," 
says  Liebig,  "that  the  yeast  consists  of  vegetable  cells 
which  come  into  existence  and  multiply  in  a  liquid  con- 
taining sugar  and  an  albuminoid  substance  (it  is  I  who 
underscore).  The  yeast  is  necessary  in  order  that  there 
may  be  formed  in  its  tissues,  by  means  of  the  albuminoid 
substance  and  the  sugar,  a  certain  unstable  combination," 
which  alone  is  capable  of  undergoing  dismemberment. 


130  pasteur:  the  history  of  a  mind 

When  the  yeast  ceases  to  grow,  "the  union  between  the 
constituent  parts  of  its  cell-contents  is  destroyed,  and  it 
is  through  the  movement  that  goes  on  there  that  the 
cells  of  the  yeast  cause  a  derangement,  or  a  separation,  of 
the  elements  of  the  sugar,  or  of  other  organic  molecules." 
And  behold  how,  even  in  the  sciences,  that  is  to  say 
where  one  is  dealing  only  with  facts,  one  can  always 
marry  the  Grand  Turk  and  the  Republic  of  Venice. 
Liebig  made  a  concession  of  words  on  condition  that 
his  opponent  would  make  to  him  a  concession  of  facts. 
"I  grant  you,"  he  said,  "that  this  is  a  vital  phenomenon 
taking  place  in  a  living  organism,  provided  you  grant 
me  that  it  is  of  a  chemical  order.  If  you  do  not  make 
this  concession,  I  shall  always  have  the  right  to  say 
that  you  have  not  looked  into  the  question  far  enough, 
that  you  have  been  arrested  before  a  closed  door  which 
I  am  trying  to  open."  The  curious  thing  is  that, 
fundamentally,  he  was  right  ;  that  the  term  vital  phenom- 
enon which  Pasteur  resolved  upon,  was  in  no  sense 
more  exact  than  Liebig' s  phrase  molecular  disintegration 
(d'ébranlement  moléculaire)  ;  that,  furthermore,  all  phe- 
nomena of  nutrition  within  the  cell  are  reduced  neces- 
sarily to  chemical  phenomena.  But  the  value  of  a 
theory  lies  not  in  the  words  which  express  it,  all  of  which 
are  necessarily  somewhat  vague;  otherwise,  absolute 
truth  and  clearness  would  be  reached  on  a  question,  and 
we  shall  never  arrive  at  that.  The  value  of  a  theory 
depends  upon  the  direction  which  it  gives  to  research. 
If  Liebig  was  perhaps  right  in  affirming  that  within 
the  cell,  in  the  deep  roots  of  the  vital  act,  his  theory  and 
that  of  Pasteur  were  blended,  one  is  astonished  to  see 
him  ignore  or  forget  that  they  are  essentially  distinct 
from  the  point  of  view  of  research  and  progress.  The 
one  theory  affirms  the  specificity  of  the  act  of  fermenta- 
tion and  incarnates  it  in  a  living  organism,  which  can 


DISCUSSION   WITH   LIEBIG  131 

be  cultivated  and  transferred  from  medium  to  medium 
with  its  specific  properties.  The  other  theory  denies 
this  fertile  specificity,  since  it  admits  again  in  1869, 
as  we  have  just  seen,  that  the  cells  of  the  yeast  can 
separate  "the  elements  of  sugar  or  of  other  organic 
molecules." 

These  two  memoirs  of  Liebig  were  translated  and 
published  in  1871  in  the  Annales  de  chimie  et  de  physique. 
I  cannot  surmise  what  procured  for  them  the  honor  of 
this  exhumation.  Pasteur  was  taken  by  surprise,  and 
replied  in  the  Comptes-rendus  de  V Académie.  The  war 
of  1870  had  just  ended,  and  his  soul  was  embittered. 
He  did  not  consider  at  all  in  these  memoirs  the  special 
pleading,  or  dissertation,  on  origins  and  causes.  He 
went  straight  to  the  facts.  Liebig  had  had  the  impru- 
dence to  gainsay  some  of  those  facts  which  troubled  him. 
He  would  not  have  it,  for  example,  that  the  yeast  could 
develop,  live  and  produce  fermentation  in  a  medium 
containing  only  sugar,  mineral  salts  and  ammonia,  as 
the  exclusive  source  of  nitrogen.  The  last  dress  given 
to  his  theory  demanded  in  addition  to  these,  as  I  have 
emphasized  above,  a  previously  elaborated  albuminous 
compound. 

In  this  respect  I  find  it  very  difficult  to  come  to  terms 
with  Liebig.  While  he  was  on  the  scent  of  philosophical 
explanations,  he  could  just  as  well  have  admitted  that 
the  yeast  itself  manufactured  in  its  own  tissues  the 
albuminoid  substance  of  which  it  had  need.  I  do  not 
see  wherein  this  conception  stood  in  the  way  of  the  final 
development  of  his  theory.  But  he  had  his  idea,  which 
the  experiments  of  Pasteur  contradicted.  He,  therefore, 
had  repeated  this  experiment  of  fermentation  in  a  mineral 
medium  and  had  not  succeeded,  because  it  is  difficult, 
and  had  concluded  that  Pasteur  was  deceived. 

He  denied,  furthermore,  that  Mycoderma  aceti  was  the 


132  pasteur:  the  history  of  a  mine 

agent  of  acetification  in  the  German  vinegar  works; 
"for,"  he  said,  "ona  wood  shaving  which  had  been 
used  for  25  years  in  a  large  vinegar  factory  in  Munich, 
there  was  no  trace  of  mycoderma  visible,  even  under  the 
microscope." 

In  the  presence  of  these  denials,  Pasteur  had  recourse 
anew  to  the  tactics  which  had  proved  so  successful  with 
Pouchet,  Joly  and  Musset.  He  demanded  that  Liebig 
present  himself,  in  company  with  him,  before  a  com- 
mission of  the  Academy  of  Sciences,  which  should  be 
charged  with  the  duty  of  pronouncing  between  them,  and 
in  the  presence  of  which  Pasteur  offered  in  the  first  place 
to  prepare,  in  an  exclusively  mineral  medium,  as  much 
yeast  of  beer  as  Liebig  could  reasonably  demand; 
in  the  second  place  he  promised  to  show  to  the  com- 
mission, and  to  Liebig  himself,  the  acetifying  mycoderma 
on  all   the  beech  shavings  of  the  factory  in  Munich. 

The  challenge  was  urgent.  Pasteur  would  not  have 
been  in  position  to  give  it  at  the  time  of  his  studies  in 
1860  on  alcoholic  fermentation.  His  cultures  of  yeast 
in  a  mineral  medium  were  at  that  time  too  poor  and  too 
uncertain,  but  since  he  had  begun  his  studies  on  beer, 
to  which  we  shall  soon  refer,  and  had  found  yeasts  ac- 
commodating themselves  to  these  mediocre  culture  con- 
ditions, he  was  sure  of  his  facts.  Liebig  did  not  accept 
the  challenge.     He  only  remained  a  little  melancholy. 

I  have  as  proof  of  this  a  letter  in  which  he  states  the 
somewhat  fallacious  idea,  that  by  going  into  the  subject 
thoroughly  enough,  Pasteur  and  he  would  have  ended  by 
discovering  and  understanding  each  other.  "I  have 
often  thought,"  he  wrote  me  in  1872,  "in  my  long  prac- 
tical career  and  at  my  age  (69  years),  how  much  pains 
and  how  many  researches  are  necessary  to  probe  to  the 
depths  a  rather  complicated  phenomenon.  The  greatest 
difficulty  comes  from  the  fact  that  we  are  too  much  ac- 


THE   DISEASES    OF   WINE  133 

customed  to  attribute  to  a  single  cause  that  which  is  the 
product  of  several,  and  the  majority  of  our  controversies 
come  from  that." 

"I  would  be  much  pained  if  M.  Pasteur  took  in  a  dis- 
paraging sense  the  observations  in  my  last  work  on 
fermentation.  He  appears  to  have  forgotten  that  I 
have  only  attempted  to  support  with  facts  a  theory 
which  I  evolved  more  than  30  years  ago,  and  which  he 
had  attacked.  I  was,  I  believe,  in  the  right  in  defending 
it.  There  are  very  few  men  whom  I  esteem  more  than 
M.  Pasteur,  and  he  may  be  assured  that  I  would  not 
dream  of  attacking  his  reputation,  which  is  so  great  and 
has  been  so  justly  acquired.  I  have  assigned  a  chemical 
cause  to  a  chemical  phenomenon,  and  that  is  all  I 
have  attempted  to  do." 

Thus  Pasteur  and  Liebig,  two  master  minds,  each 
qualified  to  grasp  the  view-point  of  the  other,  both  of 
whom  loved  science  above  all  things,  remained  divided, 
because  they  could  not  agree  on  the  rôle  of  the  yeast  in 
alcoholic  fermentation.  Is  there  not  to  be  derived  from 
this  a  great  lesson  for  scientific  men,  and  even  for  those 
who  are  not? 


IV 

THE  DISEASES  OF  WINE 

We  shall  perceive  at  once  the  advantage  of  having  the 
theories  of  Pasteur  replace  those  of  Liebig  in  science. 
Arrived  at  this  stage  of  advancement,  Pasteur  had 
before  him  a  fertile  province  which  he  could  conquer  by 
a  wave  of  the  hand,  and  which  would  have  remained 
closed  and  inaccessible  under  the  old  ideas.  I  will  ex- 
plain my  meaning. 

What  had  Pasteur  just  found  out?    That  acetifica- 


134  pasteue:  the  history  of  a  mind 

tion,  that  is  to  say  one  of  the  maladies  to  which  wine  is 
constantly  exposed,  is  exclusively  the  work  of  a  micro- 
organism. But  there  are  many  other  diseases  which 
invade  wines  with  more  or  less  rapidity.  The  wines  of 
Bordeaux  turn,  those  of  Burgundy  become  bitter,  the 
wines  of  Champaigne  become  ropy.  At  this  time,  the 
Phylloxera  had  not  yet  made  its  appearance,  and  many 
persons  had  caves;  but  there  was  no  cave  where  a  malady 
of  the  wine  did  not  appear  from  time  to  time,  and  did 
not  cause  losses,  which  were  often  grievous. 

Upon  that  point,  the  ideas  of  Liebig  shed  no  great  light. 
According  to  them,  the  wine  was  constantly  in  move- 
ment, at  work;  those  wines  which  preserved  themselves 
intact,  and  were  called  de  garde,  reached  the  end  of 
fermentation  with  a  certain  state  of  equilibrium  between 
their  sugar  and  their  organic  matter  serving  as  ferment; 
these  two  elements  were  equally  exhausted.  If  there 
had  been  too  little  ferment  in  the  beginning,  a  portion  of 
the  sugar  remained  unchanged,  and  the  wine  was  sweet, 
that  is  to  say  incomplete.  If  there  had  been  too  little 
sugar,  on  the  contrary,  some  ferment  remained  which 
continued  to  work  upon  the  substance  and  to  produce 
therein  vitiations  of  the  taste.  This  explanation,  so 
beautifully  symmetrical,  had  seduced  people's  minds, 
and  the  reader  found  it  paraphrased  in  all  the  books  on 
the  subject.  As  to  a  remedy,  it  did  not  give  any,  or  at 
least  it  had  not  done  so. 

For  Pasteur,  on  the  contrary,  these  ideas  had  no  mean- 
ing. He  was  sure  that  the  activity  of  the  yeast  was 
arrested  after  having  transformed  the  sugar,  and  that 
it  could  act  neither  upon  the  alcohol  which  it  had 
formed,  nor  upon  the  other  elements  of  the  wine.  In 
that  he  was  deceived,  for  we  have  seen  since  that  the 
yeast  can  destroy  in  time  the  glycerin  which  it  has 
produced,  just  as  the  mycoderma  of  the  vinegar  burns  the 


THE   DISEASES    OF   WINE  135 

acetic  acid  which  it  has  formed.  But,  as  usual,  Pasteur 
was  deceived  only  half  way,  and  his  deduction  was  exact. 
The  vitiations  in  taste  which  sometimes  are  observed  in 
certain  wines  could  not  result  from  any  normal  physical 
or  chemical  phenomenon,  for  the  wine  was  preserved 
almost  everywhere  in  the  same  fashion,  and  these 
changes  ought  to  be  seen  everywhere.  There  remained 
then  one  plausible  explanation,  that  is  that  these  vitia- 
tions came  from  special  fermentations,  produced  by 
special  ferments  analogous  to  the  acetic  ferment. 

Here  is  the  conclusion  to  which  the  logic  of  his  mind 
and  of  his  acquired  knowledge  led  Pasteur!  It  re- 
mained to  see  what  experimentation  would  show.  He 
had  at  Arbois,  fortunately,  some  old  comrades  of  his 
childhood  who  owned  some  caves  well  stocked  for  home 
and  market  purposes,  and  he  easily  obtained  permission 
to  subject  their  wines  to  a  microscopic  study. 

From  the  first  moment,  he  surmounted  the  difficulty. 
Every  time  that  the  tasters  pointed  out  to  him  a  par- 
ticular defect  in  taste,  he  found  so  constantly  a  distinct 
microscopic  species  mixed  with  the  yeast  in  the  bottom 
of  the  cask,  that  soon  he  was  able  to  make  the  test  in- 
versely, that  is  to  say,  to  indicate  in  advance  the  savor  of 
the  wine  by  examining  its  deposit.  The  normal  wines 
contained  only  the  yeast. 

With  a  guiding  idea,  so  clear  and  so  well  verified  by 
experiment,  he  could  begin.  After  some  months  passed 
at  Arbois  in  an  improvised  laboratory,  Pasteur  succeeded 
in  elucidating  the  question,  and,  in  1866,  he  was  able  to 
place  in  the  hands  of  the  Emperor,  who  had  encouraged 
him  in  his  researches,  a  book  containing  the  complete 
solution  of  the  problem  which  he  had  set  himself  to  solve. 

This  book  is  a  trilogy,  of  which  all  the  parts  hold  to- 
gether. In  the  first  part,  he  shows  that  all  the  maladies 
enumerated  above,  the  turning,  becoming  bitter,  becom- 


136  pasteur:  the  history  of  a  mind 

ing  oily,  which  are  not  the  sole  changes  which  wine  can 
undergo,  but  only  those  best  known,  are  each  dependent 
upon  a  special  micro-organism  which  lives  at  the  expense 
of  one  of  the  elements  of  the  wine,  and  imprints  on  this 
beverage  a  characteristic  change  of  composition  and  of 
taste.  This  is  not  the  place  to  insist  on  the  morphology 
or  the  properties  of  these  different  organisms  represented 
in  Fig.  8,  page  70.  We  will  take  from  the  history  of  the 
facts  only  what  is  necessary  to  explain  the  history  of 
the  ideas. 

The  solution  of  this  first  problem  allowed  two  others  to 
be  approached.  What  goes  on  in  a  wine  which  becomes 
old  normally,  in  the  absence  of  organisms?  What  is  it 
necessary  to  do,  in  order  that  wine  may  always  grow  old 
normally?  It  is  on  these  last  two  questions  that  some 
developments  are  necessary.  I  would  like  to  show  to 
what  degree  the  new  manner  of  regarding  them  and  of 
treating  them  rendered  them  fertile. 


V 
ACTION  OF  OXYGEN  ON  WINE 

In  the  way  in  which  it  was  stated,  the  first  question 
was  evidently  one  of  pure  chemistry,  and  Pasteur  found 
himself  brought  back  to  his  first  domain.  The  natural 
aging  of  a  wine,  when  microbes  are  absent,  can  only  take 
place  by  the  play  of  forces  within  the  liquid,  and  of 
those  which  may  result  from  its  contact  with  oxygen. 
What  did  science  and  practice  have  to  say  on  this  subject? 

The  practical  man  seemed  to  be  inspired  with  a  terror 
of  the  oxygen  of  the  air.  The  wine  was  exposed  to  the 
air  only  so  long  as  absolutely  necessary  for  the  decanting. 
It  was  the  custom  to  sulphur,  that  is  to  say,  to  fill  with 


ACTION   OF   OXYGEN   ON   WINE  137 

sulphurous  acid  the  casks  in  which  it  was  to  be  received; 
also,  in  some  portions  of  the  country,  to  fill,  that  is,  to 
keep  constantly  full,  the  casks  in  which  it  was  stored. 
It  was  said  that  it  is  more  exposed  to  the  danger  of 
spoiling  in  casks  of  permeable  wood  than  in  glass  bottles. 
It  was  well  known  that  it  became  flat  in  contact  with  the 
air,  and  recently  M.  Berthelot  had  quite  justly  related 
this  phenomenon  to  an  absorption  of  oxygen.  Bous- 
singault  had  shown,  on  his  part,  that  the  wine  of  casks 
contained  only  nitrogen  and  carbonic  acid,  that  is  to 
say,  there  is  no  longer  a  trace,  in  the  free  state,  of  the 
oxygen  which  it  has  certainly  taken  from  the  air  at  the 
same  time  as  the  nitrogen.  In  short,  for  science  as  for 
practice,  wine  seemed  to  be  a  substance  most  oxidizable 
and  unstable  in  regard  to  aeration. 

Of  that  there  was  no  doubt.  Pasteur  had  a  great 
respect  for  secular  practices  and  said  that  science  ought 
not  to  condemn  them  lightly,  but  that  it  had  always  the 
right  to  search  for  their  interpretation.  It  might  be 
that  the  wine  was  really  unable  to  endure  contact  with 
air,  but  also  it  might  be  that  air  is  necessary  to  the 
microbes  which  menace  the  wine,  and  that  to  deprive 
it  of  the  air  would,  in  a  measure,  guarantee  it  against 
disease. 

Pasteur  had  already  arrived  at  a  stage  where  he  could 
accept  only  the  second  of  these  two  interpretations.  He 
knew  from  his  experiments  on  spontaneous  generations, 
how  little  organic  substances  are  oxidizable  without  the 
intervention  of  microbes,  and  on  the  other  hand,  he  had 
just  seen  that  the  acetic  ferment  which  constantly 
threatens  wines  with  acetification  has  great  need  of  oxy- 
gen. Furthermore,  while  he  was  studying  this  myco- 
derma  of  vinegar  he  had  also  studied  another  superficial 
pellicle,  that  which  forms  so  easily  on  the  surface  of 
wine  left  behind  in  filling  the  bottles  and  which  resem- 


138  pasteur:  the  history  of  a  mind 

bles  the  preceding  in  its  need  of  oxygen — the  mycoderma 
of  wine. 

The  latter,  although  it  is  more  frequent  than  the 
mycoderma  of  vinegar,  nevertheless  has  less  grievous 
effects,  because,  not  stopping  half  way,  it  pushes  quite 
to  term  the  oxidation  of  the  alcohol,  and  makes  out  of 
it  immediately  water  and  carbonic  acid.  This  carbonic 
acid  replaces  the  oxygen  absorbed  from  the  air,  and  by 
reestablishing  the  pressure,  prevents  a  new  influx  of  air 
and  of  oxygen.  Thus  the  development  of  the  myco- 
derma of  the  wine,  which  takes  place  on  the  surface  of 
all  the  casks  which  are  not  full,  ordinarily  passes  unper- 
ceived,  although  sometimes  the  layer  which  covers  the 
liquid  may  be  thick.  When  it  has  exhausted  all  the 
oxygen  which  exists  above  it  in  the  closed  cask,  it  renews 
its  supply  only  slowly;  and  when  this  happens  it  con- 
sumes it  entirely  and  leaves  no  trace  of  it,  in  a  free  state, 
in  the  liquid  below.  It  is  an  impenetrable  filter  for  the 
oxygen,  as  impenetrable  as  a  wall  of  glass. 

That  granted,  did  the  practices  employed  in  wine- 
making  favor  the  wine  or  its  parasites?  In  examining 
the  question  from  this  entirely  new  point  of  view,  Pasteur 
was  not  slow  in  recognizing  that,  far  from  being  formid- 
able to  the  wine,  it  is  the  oxygen  which  makes  it,  which 
takes  away  the  acid  and  rough  taste  of  new  wine,  and 
which  makes  it  more  and  more  fit  to  drink.  It  is  also 
the  oxygen  which  divests  it  little  by  little  of  its  coloring 
matter,  yellows  what  is  left,  and  gives  to  it  gradually 
that  onion-skin  tint,  with  which  our  ancestors  were 
familiar,  and  of  which  we  are  ignorant,  because  they 
knew  the  worth  of  life,  and  we  know  only  its  cost. 
Finally,  as  its  action  increases,  the  oxygen,  after  having 
given  to  the  wine  the  taste  of  old  wine,  ends  by  consum- 
ing it  and  spoiling  it.  When  he  had  studied  a  subject 
Pasteur  loved  to  sum  up  the  ideas  which  he  had  ac- 


ACTION   OF   OXYGEN   ON   WINE 


139 


quired  in  the  form  of  some  startling  experiments  which 
at  the  same  time  furnished  a  verification  of  his  ideas, 
and  constituted  a  classical  demonstration.  Here  are 
some  which  were  used  to  illustrate  this  subject. 

Suppose  at  the  end  of  the  fermentation,  at  the  time 


Submerged. 


Fig.  13. — Mycoderma  of  wine. 

In  the  state  of  flowers  of  wine. 


when  the  wine,  already  clear,  is  still  saturated  with 
carbonic  acid,  we  fill  a  bottle  full  in  such  a  way  that  at 
no  time  during  the  process  does  the  wine  come  into  con- 
tact with  the  air.  This  operation  ended,  the  bottle  is 
hermetically  sealed  by  melting  wax  over  the  stopper. 
The  wine  thus  treated  remains  indefinitely  as  it  was  at 


140  pasteur:  the  history  of  a  mind 

the  moment  of  drawing  off;  it  preserves  its  color;  its 
savor  does  not  change  to  any  appreciable  degree;  it  takes 
on  no  particular  bouquet;  it  is  always  new  wine.  During 
this  time,  the  rest  of  the  same  wine,  preserved  in  a  cask 
and  subject  to  the  ordinary  manipulations,  becomes  old 
in  the  complex  sense  which  one  ordinarily  gives  to  this 
word.  What  differences  are  there  then  between  the  two 
wines?  One  only:  under  its  envelope  of  glass  the 
former  has  not  been  subject  to  the  action  of  the  oxygen 
of  the  air  which  filters  constantly  and  slowly  through 
the  barrel  staves,  and  which,  combining  with  the  wine, 
determines  its  ripening. 

Without  taking  any  particular  precautions  to  avoid 
excess  of  air,  let  us  repeat  the  experiment  which  I 
have  just  described,  leaving  the  bottle  half  empty  and 
closed  with  its  stopper.  While  the  wine  in  the  previous 
experiment  remained  young,  that  in  the  new  bottle 
clouds  and  gives  an  amorphous  deposit  which  increases 
little  by  little  and  finally  adheres  to  the  walls.  It  is  the 
red  coloring  matter  which  has  separated  from  the  wine. 
At  the  same  time,  the  oxygen  left  in  the  bottle  dis- 
appears, and  the  wine  changes,  loses  its  original  savor, 
becomes  old,  and  takes  on  in  a  high  degree  the  taste 
of  rancio, x  if  it  is  red,  of  madeira  if  it  is  white.  It  may 
even  fade  away  and  disappear  altogether,  if  there  is 
too  little  of  it  in  proportion  to  the  oxygen. 

The  essential  act  in  the  aging  of  wine  is,  therefore,  its 
slow  combination  with  oxygen.  When  the  absorption 
of  oxygen  is  too  rapid,  the  wine  becomes  vapid,  but  this 
is  a  passing  phenomenon,  and  it  is  often  sufficient  to 
let  the  wine  alone  for  this  taste  to  disappear,  as  soon 
as  the  oxygen  absorbed  in  a  gaseous  state  has  served 
in^the  wine  for  the  oxidations  which  have  consumed  it. 

1  Old  wine  which  has  acquired  the  taste  of  Spanish  wines.     TVs. 


PASTEUR 


(Courtesy  of  Dr.  Winford   H.   Smith,    Superintendent,  Johns 
Hopkins  Hospital.) 


THE   HEATING   OF   WINES  141 

VI 
THE  HEATING  OF  WINES 

These  facts  being  formulated  and  established  in  the 
first  two  parts  of  the  Études  sur  les  Vins,  the  third  part 
appears  as  a  dénouement.  The  diseases  of  wine  are 
correlative  with  the  development  of  parasitic  vegeta- 
tions; it  is  the  fear  of  these  parasites  which  burdens 
all  the  practices  of  wine-making  and  the  preservation  of 
wine,  and  forbids  the  employment  of  other  methods 
more  favorable  to  the  aging.  If  we  can  succeed  in 
eliminating  these  dangerous  ferments,  or  in  destroying 
them  when  they  are  present,  we  shall  have  overcome 
this  antinomy  and  have  solved  the  problem. 

It  is  here  that  Pasteur  found  once  more  the  advantage 
of  his  earlier  studies,  for  it  is  remarkable  that,  save  from 
himself,  he  borrowed  almost  never.  We  have  seen  this 
in  what  precedes.  It  will  be  still  more  apparent  as  we 
advance. 

The  problem  was  to  prevent  or  to  arrest  the  develop- 
ment of  the  parasites  without  in  any  way  changing 
the  constitution  of  the  wine.  For  this  purpose  he  had 
at  his  disposition  the  action  of  antiseptics  or  that  of 
heat.  He  tried  antiseptics  first,  especially  the  hypo- 
phosphites  and  the  bisulphites  of  the  alkalin  metals, 
which  are  without  decided  odor  and  taste  when  they 
are  in  dilute  solution,  and  which  become  inoffensive 
phosphates  or  sulphates  after  having  absorbed  oxygen. 
The  results  were  mediocre  or  negative.  It  was  then  that 
he  thought  of  the  action  of  heat. 

We  understand  his  hesitations  in  having  recourse 
to  this  agent.  By  means  of  it  he  was  sure  of  killing  the 
microbes  without  even  heating  to  the  boiling  point, 
for  wine  is  an  acid  liquid,  and  the  acidity  helps  on  the 


142  pasteur:  the  history  of  a  mind 

action  of  heat,  as  we  have  seen  when  considering  spon- 
taneous generations.  Moreover,  there  was  a  chance, 
and  Pasteur  had  not  failed  to  perceive  this  possibility, 
that  it  might  not  be  necessary  to  kill  the  ferments, 
which,  considering  the  slowness  with  which  they  or- 
dinarily develop,  are  under  unfavorable  conditions  in  the 
wine.  To  weaken  them  by  the  heating  so  that  they  could 
not  multiply  would  perhaps  be  sufficient.  All  this  was 
encouraging.  But,  on  the  other  hand,  the  employment 
of  even  a  minimum  quantity  of  heat  appeared  to  have 
its  grave  dangers.  Everybody  has  drunk  warm  wine 
and  knows  that  it  is  no  longer  wine.  Those  ancestors 
whom  we  invoked  a  short  while  back  recommended 
one  to  drink  cooled  wine.  Only  Bordeaux  wine,  they 
added,  is  improved  by  conveying  it  into  the  dining  room 
four  hours  in  advance  of  the  guests. 

Yes,  Pasteur  might  have  replied  to  these  objections: 
but  all  those  wines  which  one  hesitates  to  heat  are  wines 
recently  drawn  off  and  aerated.  Would  it  be  the  same 
for  the  bottles  which  would  be  heated  only  after  having 
allowed  their  contents  time  to  transform  into  combined 
oxygen  the  gaseous  oxygen  absorbed  during  the  racking? 
No  one  could  reason  more  correctly,  and  it  is  thus  that 
Pasteur,  at  the  first  step,  and  almost  without  groping, 
by  proceeding  always  in  the  direct  light  of  his  former 
experiments,  reached  that  procedure  of  heating  to 
55°  C.  for  which  such  a  noble  future  seemed  reserved 
when  it  first  appeared. 

At  this  time,  in  1867,  the  prosperity  of  viticulture 
was  great;  France  reckoned  more  than  2  million  hectares 
planted  in  vines  and  her  wines,  the  dissemination  of 
which  was  favored  by  commercial  treaties,  seemed 
destined  to  reach  all  the  markets  of  the  world.  To  give 
to  an  industry  operating  upon  50  million  hectolitres, 
and  worth  500  million  francs,  the  means  of  avoiding 


THE   HEATING   OF   WINES  143 

the  deterioration  of  its  merchandise  and  of  increasing 
more  rapidly  its  commercial  value,  was  a  public  benefit. 

Unfortunately,  two  years  previous,  on  the  plateau  of 
Pujaut  in  Gard,  there  had  appeared  the  Phylloxera  which 
has  since  caused  so  much  devastation,  and  the  following 
year  the  insect  had  disseminated  its  colonies  over  a 
large  portion  of  the  departments  of  Vaucluse  and 
Bouches-du-Rhône.  Another  microbial  power  had  taken 
a  hand,  against  which  science  and  agriculture  were  at 
this  time  unarmed.  Consequently,  for  some  years 
Pasteur's  method  was  ruined.  No  one  need  consider 
how  to  keep  grains  in  a  time  of  famine,  and  the  heating 
of  wines  was  little  practised  except  for  those  which  must 
be  shipped  under  bad  conditions  as  to  keeping,  for  ex- 
ample, in  the  commissariat  of  the  Navy. 

But  now  they  return  to  it  gradually  in  the  wine  indus- 
try, and  for  some  years  it  has  been  employed  regularly  in 
the  beer  traffic,  with  the  best  results.  It  has  done  more, 
it  has  entered  into  the  language,  and  the  word  pasteur- 
ize signifies,  even  outside  of  France,  to  protect  against 
microbes  by  the  action  of  heat.  We  pasteurize  wine, 
milk,  and  beer,  and  are  right  in  performing  the  operation, 
and  in  so  calling  it. 

I  would  be  through  with  the  subject  if  it  were  not  for 
saying  a  word  or  two  on  the  claims  of  priority  raised 
against  Pasteur,  and  on  the  somewhat  bitter  polemic 
which  resulted.  It  is  always  wrong  to  confide  one's 
rancors  and  jealousies  to  the  public.  We  do  not  recollect 
sufficiently  that  this  public  has  its  own  affairs,  is  only 
moderately  interested  in  the  fundamentals  of  the  debate, 
and  contents  itself  with  being  amused  at  the  blows. 
Pasteur  had  the  best  side  here  and  should  have  been 
content  with  shrugging  his  shoulders.  He  was  accused 
of  having  re-invented  the  process  of  Appert,  as  if  there 
could  be  the  least  parity  between  the  empiricism  of  the 


144  pasteur:  the  history  of  a  mind 

one  and  the  experimental  logic  of  the  other.  Appert 
had  taught  us  only  one  thing,  viz.,  that  sometimes  wine 
could  be  warmed  without  changing  the  taste,  or  becom- 
ing heated  wine.  If  Pasteur  had  known  of  this  experi- 
ment, he  would  have  hesitated  less  than  he  did  in  having 
recourse  to  the  action  of  heat,  but  his  work  would  have 
remained  the  same.  Besides,  he  made  haste,  as  soon  as 
he  knew  of  them,  to  render  to  Appert's  experiments  the 
credit  they  deserved. 

It  was  also  said  to  him,  in  all  manner  of  ways,  that  the 
heating  of  wines  had  been  known  and  esteemed  for  a 
long  time  at  Mèze,  in  the  department  of  Hérault,  near 
Cette.  "So  be  it,"  answered  Pasteur,  who  had  gone  to 
see,  "they  do  warm  the  wine  at  Mèze,  but  it  is  to  age  it 
more  speedily.  For  this  purpose  they  warm  it  in  con- 
tact with  the  air,  for  a  long  time,  so  as  to  bring  about 
changes  in  taste,  which  sometimes  exceed  the  limit,  and 
which  it  is  then  necessary  to  correct;  these  gropings 
about  in  the  dark  show  that  the  wine  merchants  of  Mèze 
do  not  have  any  clear  idea  of  what  they  are  about,  and 
have  not  read  my  book.  It  would  be  to  their  interest  to 
do  so,  for  I  give  the  theory  of  their  practice.  Mean- 
while, what  has  this  long  and  dangerous  warming  in 
contact  with  the  air  in  common  with  that  rapid  heating 
to  50°C,  protected  from  the  air,  which  I  recommend?" 

There  remains  finally  the  laggard  claim  of  M.  de  Ver- 
gnette-Lamotte,  but  this  is  so  strange  and  shows  such 
ignorance  of  the  subject,  that  it  is  better  not  to  speak  of 
it.  It  resulted  in  some  bitter-sweet  notes  which  may  be 
read  in  the  Comptes  rendus  de  l'Académie  des  Sciences  and 
in  the  Moniteur  scientifique  de  Quesneville.  All  profound 
faith  is  necessarily  a  little  intolerant,  and  Pasteur  had 
that  faith. 


PASTEUR 

(From  a  woodcut  in  "Jour.  d'Agric.  pratique/'  1895.) 


FIFTH  PART 
Studies  on  the  Diseases  of  Silkworms 

I 
ORIENTATION  TOWARDS  PATHOLOGY 

I  still  recall  the  day  when  Pasteur,  returning  to  the 
laboratory,  said  to  me  with  some  emotion  in  his  voice: 
"  Do  you  know  what  M.  Dumas  has  just  asked  me  to  do? 
He  wants  me  to  go  into  the  South  and  study  the  disease 
of  silkworms."  I  do  not  recall  my  reply;  probably  it 
was  that  which  he  had  made  himself  to  his  illustrious 
master:  "Is  there  then  a  disease  of  silkworms?  and 
are  there  countries  ruined  by  it?"  This  took  place  so 
far  from  Paris!  and  then,  also,  we  were  so  far  from  Paris, 
in  the  laboratory  ! 

However  that  may  be,  Pasteur  had  reached  one  of  the 
turning  points  of  his  life.  For  a  long  time  he  had  had  a 
presentiment  that  all  the  new  ideas  he  had  introduced 
into  science  might  be  of  importance  for  the  physiology 
and  pathology  of  the  higher  animals.  For  a  long  time 
the  two  notions  of  fermentation  and  disease  had  been 
connected,  as  we  have  seen  during  our  consideration  of 
spontaneous  generations.  But  this  relation  had  become 
closer  since  it  had  been  known  that  it  was  living  cells 
which  presided  over  the  processes  of  fermentation. 
However,  let  us  keep  from  believing  that  the  logic  of 
the  ideas  of  Pasteur  led  him,  at  this  time,  to  the  spot 
where  we  see  him  so  naturally  to-day,  namely  to  the  con- 
clusion that  disease  could  result  from  the  development, 
in  the  normal  tissues,  of  a  living  microscopic  organism, 
10  145 


146  pasteur:  the  history  of  a  mind 

the  cause  of  the  disease.  That  is  the  idea  divested  of  all 
its  trappings — an  idea  reached  ordinarily  only  after 
one  has  made  the  tour  of  ideas  much  more  complicated. 
In  fact,  as  we  shall  see,  Pasteur  reached  this  conclusion 
only,  so  to  speak,  in  spite  of  himself,  and  after  two  years 
of  study. 

He  was,  it  seems,  more  disposed  to  believe  at  this 
moment  that  the  disease,  whatever  it  might  be,  could 
by  modifying  the  fluids  of  the  body  prepare  the  soil 
for  this  or  that  microbe,  which  was  then  according  to  the 
case,  either  the  result  of  the  disease,  or  the  visible  evi- 
dence of  it,  or  the  beginning  of  a  new  disease.  We  shall 
see  later  that  these  notions  are  not  as  exclusive  of  the 
other  idea  as  one  might  at  first  sight  believe  them  to  be. 
In  all  cases,  they  ended  with  a  repercussion  of  the  microbe 
on  its  host,  and  it  was  for  this  reason  that  Pasteur  main- 
tained for  so  long  a  time  the  relations  between  the  phy- 
siology of  the  ferments  and  that  of  the  higher  animals. 
Thus  we  have  seen  him  liken  the  red  blood-corpuscle 
to  the  acetic  ferment  which,  like  the  latter,  can  take 
the  oxygen  from  the  air  and  carry  it,  endowed  with  a 
more  powerful  activity,  to  the  combustible  substance. 

But  when  there  was  raised  the  question  of  going  farther 
and  of  actually  coming  into  contact  with  the  higher 
animals,  Pasteur  hesitated.  He  was  not  a  physiologist. 
To  no  purpose  did  we  go  to  hear  the  course  of  Claude 
Bernard,  where  he  took  notes  feverishly.  It  would  have 
been  necessary  for  him  to  become  a  new  soul,  and  he  had 
neither  the  time  for  it  nor  the  patience.  The  insist- 
ance of  Dumas  had  just  placed  him  face  to  face  with 
an  experience  which  he  both  desired  and  dreaded,  and 
if  his  self-distrust  had  made  him  hesitate,  at  the  first 
encounter,  in  reality,  the  attraction  for  the  unknown  and 
a  certain  interior  voice  urged  him  to  accept. 

Consequently,   his   decision  was  soon  made.     After 


OKIENTATION   TOWAEDS   PATHOLOGY  147 

having  acquired  a  fragmentary  knowledge  of  the  general 
structure  of  the  larvae  of  insects  by  causing  to  be  dissected 
in  his  presence  a  white  worm  [larva  of  the  May  beetle] 
or  a  larva  of  Oryctes  nasicornis,  after  having  assisted  at 
some  sittings  of  an  Imperial  Commission  on  Silk  Culture 
from  which  he  came  away  more  discouraged  than  en- 
lightened, after  having  skimmed  the  last  published  books 
on  the  subject,  he  set  out  for  the  South.  It  was  at  the 
beginning  of  June:  the  cultures  of  the  silkworms  were 
almost  completed.  From  this  fact  he  might  have  plead 
for  more  time  and  the  putting  off  of  his  investigations 
until  the  following  year,  but  his  master,  M.  Dumas,  had 
spoken:  he  was  also  more  eager  than  he  himself  suspected 
to  enter  into  this  new  world,  and  he  desired  to  begin  the 
work  at  once. 

To  it  he  devoted  six  years,  which  it  will  not  be  unprof- 
itable to  describe  in  detail,  and  that  for  two  reasons. 
The  first  is  that  nothing  can  be  more  curious  than  to  see 
Pasteur  at  close  quarters  with  a  bristling,  complicated 
question,  beginning  by  being  deceived  about  it,  by  seeing 
things  the  wrong  side  to,  but  led  back  continuously  to 
the  truth  by  experiment,  and  ending  by  unravelling  all 
the  obscurities.  I  do  not  know  a  more  beautiful  example 
of  scientific  investigation.  The  second  reason  is  that  it 
is  the  first  camp  on  a  route  wherein  he  found  immor- 
tality. The  other  discoveries  had  given  him  only  glory. 
Finally,  I  would  like  to  add,  as  a  third  reason,  that  this 
period  of  his  life  is  that  of  which  it  is  easiest  to  write 
the  history,  both  because  of  the  impressions  it  has  left 
on  those  who  helped  him  in  his  labors,  and  because  of 
the  documents  he  has  himself  published. 
jy  In  this  part  of  his  researches  he  had  not  the  right  to 
keep  the  Olympian  silence  with  which  he  loved  to  sur- 
round himself  until  the  day  in  which  his  work  seemed  to 
him  ripe  for  publicity.     He  said  not  a  word  about  it,  even 


148  pasteur:  the  history  of  a  mind 

in  the  laboratory,  where  his  assistants  saw  only  the  ex- 
terior and  the  skeleton  of  his  experiments,  without  any 
of  the  life  which  animated  them.  Here,  on  the  contrary, 
he  was  under  obligation  as  soon  as  he  had  found  out 
something  to  speak  and  to  excite  the  public  judgment 
and  that  of  industrial  practice  on  all  his  laboratory 
discoveries. 

A  hard  necessity,  that  of  laboring  thus  under  the  public 
eye,  with  an  official  connection,  in  the  presence  of  a  men- 
acing danger  which  one  has  been  commissioned  to  exor- 
cise! to  be  sent  to  combat  a  conflagration,  and  not  to 
know  where  the  fire  is,  and  not  to  have  any  pumps  !  One 
must  be  a  Pasteur  to  accept  such  a  responsibility  and 
carry  it  off  successfully.  In  any  event,  we  owe  to  this 
condition  of  things  a  multiplicity  of  documents:  reports 
to  the  Academy  of  Sciences,  to  the  Minister  of  Agri- 
culture, letters  to  M.  Dumas,  communications  to  the 
journals  of  silk  culture,  and  we  can  make  use  of  all  these 
signed  writings  of  Pasteur  to  reconstruct  the  history  of 
his  thought.  He  has  himself  authorized  us  to  consult 
them  by  inserting  them  at  the  end  of  the  second  volume 
of  his  Études  sur  la  maladie  des  vers  à  soie.  "I  might 
have  dispensed  with  reproducing  in  toto  these  pub- 
lications," he  says,  "  since  the  first  volume  contains  the 
definite  expression  of  my  actual  ideas;  but  I  have  thought 
that  they  might  be  of  some  historical  interest  and  serve 
as  an  example  in  a  difficult  and  long-winded  subject 
of  the  progressive  march  of  ideas  in  proportion  as  the 
observer  multiplies  his  experiments. 

'"Let  us  gather  together  some  facts  in  order  to  have 
some  ideas'  said  Buff  on.  It  is  not  without  utility  to 
show  to  the  man  of  the  world  or  to  the  practical  man 
at  what  cost  science  conquers  principles  the  simplest  and 
most  modest  in  appearance."1 

1  Étude  sur  la  maladie  des  vers  à  soir,  t.  II,  p.  155. 


THE    CORPUSCULAR   DISEASE    [pÉBRINE]  149 

We  shall  see  that  Pasteur  has  nothing  to  lose  from  this 
attentive  study  of  the  progress  of  his  mind.  He  some- 
times wandered  in  his  research,  as  we  have  said,  allowing 
himself  to  be  deceived  by  false  gleams,  but  he  always  re- 
turned to  the  right  path,  and  it  is  just  this  struggle  with 
error,  always  imminent,  that  makes  the  interest  of 
this  study. 


II 
THE  CORPUSCULAR  DISEASE  [PÉBRINE] 

Some  preliminary  notions  and  details  are  necessary 
to  understand  thoroughly  the  moving  vicissitudes  of 
this  struggle  against  a  scourge  as  redoubtable  as  was 
the  disease  of  silkworms  at  this  time.  Everybody  knows, 
at  least  in  a  general  way,  the  principal  phenomena  of  the 
life  of  the  silkworm:  its  birth  from  an  egg,  whose  re- 
semblance to  certain  vegetable  seeds  has  led  to  its  being 
given  the  name  of  graine;  and  its  four  molts  or  changes 
of  skin,  during  which  the  worm  ceases  to  eat,  remains 
motionless,  seems  to  sleep  upon  its  litter  [feeding  place], 
and  clothes  itself,  under  its  old  skin,  with  a  new  supple 
and  elastic  skin,  which  allows  to  it  a  new  development. 
The  fourth  of  these  molts  is  followed  after  two  or  three 
days  by  a  period  of  extreme  voracity  during  which  the 
worm  increases  in  volume  rapidly  and  acquires  its 
maximum  size  :  it  is  the  big  gorge.  This  period  terminated, 
the  worm  eats  no  more,  moves  about  uneasily,  and  if 
sprigs  of  heather  on  which  it  can  ascend  are  offered,  it 
hastens  to  choose  thereon  a  suitable  place  to  spin  its 
cocoon,  a  kind  of  silky  prison  which  permits  it  to  undergo 
in  peace  its  transformation  first  into  a  chrysalis,  and 
then  into  a  moth.  In  this  cocoon,  the  body  of  the  worm, 
emptied  of  all  the  silky  matter,  contracts  and  covers 


150  pasteur:  the  history  of  a  mind 

itself  with  a  resistant  tunic,  in  the  interior  of  which  all 
the  tissues  seem  to  fuse  into  a  pulp  of  homogeneous  ap- 
pearance. It  is  in  the  midst  of  this  magma  that,  little 
by  little,  the  tissues  of  the  moth  are  formed  and  become 
differentiated. 

The  moth  has  only  a  rudimentary  digestive  canal, 
for  it  no  longer  has  any  need  of  eating:  the  worm  has 
eaten  for  it.  It  has  wings,  but,  in  our  domestic  races,  it 
makes  no  use  of  them.  It  is  destined  only  for  the  re- 
production of  the  species,  and  the  sex-union  takes 
place  as  soon  as  it  comes  out  of  the  cocoon.  The  female 
then  lays  a  very  considerable  number  of  eggs,  which 
may  reach  600  or  800  and  in  the  races  that  we  call  annual, 
which  are  the  most  sought  after,  this  "graine"  does 
not  hatch  the  same  year  as  its  production.  It  is  de- 
layed till  the  reawakening  of  vegetation  the  spring  of 
the  following  year. 

It  is  only  when  the  grower  wishes  to  have  "graine"  or 
to  induce  the  laying  of  eggs  {faire  grainer)  that  he  awaits 
this  coming  forth  from  the  cocoon,  in  which  the  trans- 
formation of  the  worm  into  a  moth  requires  about  15 
days.  By  adding  thereto  the  35  or  40  days  required 
for  the  culture  of  the  worm,  and  the  time  necessary  for 
the  laying  of  the  eggs,  we  see  that  the  complete  evolution 
of  the  silkworm,  from  the  egg  around  to  the  egg  is  about 
two  months.  The  period  of  industrial  life  is  sensibly 
shorter.  When  the  grower  wishes  to  use  only  the  cocoons, 
he  must  not  wait  till  the  moth,  in  coming  forth,  has 
opened  them  and  thereby  rendered  them  unfit  for 
spinning.  They  are  smothered  5  or  6  days  after  they  have 
climbed  the  heather  twigs.  That  is  to  say,  the  cocoons 
are  put  into  a  vapor  bath  in  which  the  chrysalids  are 
killed  by  the  heat.  For  the  silk  grower,  in  this  case, 
scarcely  six  weeks  separate  the  time  of  egg-hatching 
from  the  time  when  he  carries  his  cocoons  to  market — 


THE    CORPUSCULAR   DISEASE    [pÉBRINE]  151 

the  time  when  he  sows  from  the  time  when  he  reaps. 
As  formerly  the  harvest  was  almost  certain  and  quite 
lucrative,  the  time  of  the  silkworm  was  a  time  of  festival 
and  of  joy,  in  spite  of  the  fatigues  which  it  imposed,  and 
in  gratitude  the  mulberry  tree  had  received  the  name  of 
arbor  d'or  from  the  populations  who  lived  upon  it. 

Unfortunately,  silk  culture  had  been  attacked  for  20 
years  by  a  cruel,  inexplicable  disease,  which  owing  to 
its  singular  behavior  and  multiple  and  changing  mani- 
festations, disconcerted  the  reason  and  baffled  the  efforts 
best  calculated,  in  appearance,  to  overcome  it.  If, 
for  example,  a  culture  of  worms  had  succeeded  very  well 
so  as  to  excite  the  admiration  of  all  the  surrounding 
country:  instead  of  smothering  it  to  wind  the  cocoons 
for  silk,  it  was  saved  for  the  egg-laying  in  a  very  natural 
hope  of  obtaining  therefrom  excellent  "graine."  But 
alas!  It  happened  that  almost  always  this  hope  was 
deceived  and  that  the  following  year  the  worms  derived 
from  these  eggs,  instead  of  growng  rapidly  like  their 
ancestors,  and  preserving  to  the  end  a  perfect  uniformity, 
acquired  slowly  the  most  diverse  sizes.  Many  died  in  the 
first  stages,  and  those  which  had  passed  the  fourth  molt 
successfully  seemed  but  little  able  to  pass  beyond  it; 
they  became  smaller,  seemed  to  melt  away,  little  by 
little,  and  ended  by  disappearing  almost  altogether, 
giving  only  a  negative  or  insignificant  yield.  The  im- 
possibility of  obtaining  good  eggs  which  was  soon  demon- 
strated by  similar  failures  with  our  fine  French  races,  had 
led  numerous  silk  growers  to  travel  seeking  healthier  eggs 
at  a  distance;  but  the  disease  seemed  to  have  made  the 
tour  of  the  world  along  with  them,  and  their  exotic 
"  graines,  "  after  having  succeeded  one  or  two  years  in 
France,  were  struck  with  sterility  both  in  our  own 
country  and  in  the  lands  where  they  originated. 

On  account  of  its  occurrence  in  cultures  which  it  ap- 


152  pasteur:  the  history  of  a  mind 

peared  should  be  the  most  robust,  the  disease  seemed 
to  be  epidemic,  and  on  account  of  its  slow  and  regular 
progress,  from  our  country  toward  the  most  distant 
regions  of  Europe  and  Asia,  it  seemed  to  present  in 
the  highest  degree  the  contagious  character:  and  yet 
other  facts,  not  less  numerous,  and  not  less  convincing 
in  appearance,  bore  witness  that  it  was  neither  epidemic 
nor  contagious.  I  will  cite  only  one  of  them,  which 
Pasteur  had  learned  at  the  beginning  of  his  studies, 
and  which  had  troubled  him  somewhat.  In  the  culture 
of  a  mixture  of  two  "graines,"  the  one  giving  white 
cocoons  and  the  other  yellow  ones,  it  had  been  observed 
that  the  first  died  almost  completely,  while  the  other 
gave  a  very  satisfactory  harvest. 

The  uncertainty  was  not  less  great  if  one  sought  to 
study  the  disease  by  itself,  without  being  preoccupied 
any  more  with  its  nosological  character.  Thus,  de 
Quatrefages,  after  having  made  a  careful  study,  believed 
himself  able  to  characterize  it  by  the  existence  in  the 
interior  and  especially  upon  the  skin  of  the  worm,  of  very 
small  spots  resembling  grains  of  black  pepper,  and  for  this 
reason  had  been  led  to  name  it  pebrine.  But  experiment 
showed  that  the  worms  could  be  spotted  without  being 
sick,  and  on  the  other  hand  that  worms  which  were 
not  spotted  did  not  necessarily  give  good  eggs.  If  one 
wished  to'  enter  further  into  the  study  of  the  disease, 
he  found  himself  in  the  presence  of  contradictory  results 
obtained  by  various  physiologists.  For  example,  Lebert 
and  Frey  had  established  that  in  the  interior  of  all  the 
diseased  worms  and  all  the  diseased  moths  there  existed 
in  abundance  a  peculiar  parasite,  the  corpuscle,  visible 
only  under  the  microscope,  observed  for  the  first  time 
by  Guérin-Mèneville,  and  the  importance  of  which 
from  the  pathological  point  of  view  had  been  caught  sight 
of  by  Cornalia.     But  if  one  believed  Philippi,  another 


THE    CORPUSCULAR   DISEASE    [PEBRINE]  153 

scientific  man,  these  corpuscles  existed  normally  in  all 
the   moths. 

A  real  progress  had,  however,  been  realized  the  day 
that  Osimo  had  discovered  the  corpuscles  in  the  eggs 
of  silkworms,  and  the  day  Vittadini,  after  having  rec- 
ognized that  their  number  increased  in  a  laying  of 
eggs  in  proportion  as  they  approached  the  period  of 
hatching,  had  based  a  method  of  distinguishing  the 
good  from  the  bad  upon  a  microscopic  examination  of  the 
eggs.  The  corpuscle  is,  indeed,  actually,  as  we  shall 
see,  the  cause  of  the  disease,  and  an  egg  which  contains 
it  can  never  give  cocoons;  but  these  two  facts  not  being 
demonstrated,  uncertainty  existed  as  to  the  theoretic 
value  of  the  procedure.  As  to  the  practice,  it  often 
gave  out  detestable  eggs  for  good  ones,  and  when  it 
condemned  the  eggs  it  was  in  the  name  of  principles  so 
uncertain  that  the  silk  grower  could  not  be  held  culpable 
for  having  no  confidence  in  the  advice  of  science. 

The  same  Osimo,  in  1859,  had  endeavored  to  push 
science  and  practice  in  another  direction.  He  had  ad- 
vised examination  not  only  of  the  eggs  but  also  of  the 
chrysalids,  and  rejection  of  the  layings  of  those  stocks 
which  were  found  too  corpuscular.  This  time  it  would 
have  been  to  approximate  correct  procedure,  as  we  shall 
see  immediately,  but  this  advice,  given  offhand,  and 
without  experimental  support,  had  been  followed  and 
tested,  offhand  also,  by  Cantoni,  who,  after  having 
cultivated  the  eggs  coming  from  non-corpuscular  moths, 
had  seen  the  worms  become  corpuscular  during  the 
culture,  which  proved,  he  had  concluded,  that  "the 
microscopic  examination  of  moths  was  also  unfortunately 
as  worthless"  as  the  other  remedies. 

By  good  fortune,  of  all  this  past  history,  of  all  this 
mixture  of  truth  and  falsehood,  Pasteur  knew  nothing 
at  the  beginning  of  his  studies.     To  his  complaint  of 


154  pasteur:  the  history  of  a  mind 

not  being  familiar  with  the  subject,  Dumas  had  replied 
one  day:  "So  much  the  better!  For  ideas,  you  will 
have  only  those  which  shall  come  to  you  as  a  result  of 
your  own  observations!"  Such  a  reply  is  not  always 
a  paradox,  but  one  must  be  careful  to  whom  he  makes  it. 


Ill 
STUDIES  OF  1865 


The  first  act  of  Pasteur  on  reaching  the  South  was  to 
seek  this  famous  corpuscle,  which  he  had  never  seen. 
He  had  no  trouble  in  finding  it.  In  the  neighborhood  of 
the  little  city  of  Alais,  in  which  he  had  installed  himself, 
all  of  the  cultures,  already  near  their  end,  were  infected. 
Sick  worms  and  moths  showed  the  corpuscles  by  thou- 
sands. Some  rare  worms  of  healthy  appearance  did  not 
show  any.  What  seemed  especially  to  result  from  this 
first  rapid  examination  was  the  exactitude  of  the  relation 
pointed  out  by  de  Quatrefages  between  the  existence  of 
the  corpuscles  and  the  presence  on  the  surface  of  the  skin 
of  the  black  spots  of  the  pébrine.  All  the  worms  hav- 
ing pébrine  showed  corpuscles  in  enormous  numbers. 
But  this  fact,  even  though  it  might  have  been  more 
thoroughly  settled  than  it  was  really,  did  not  signify 
very  much.  In  continuing  his  researches,  a  little  at 
random,  Pasteur  one  day  encountered  one  of  those 
unexpected  facts  which  it  is  so  useful  and  so  dangerous 
to  find  on  our  pathway,  when  we  begin  any  research 
whatsoever.  They  have  a  sphinx-like  physiognomy,  and, 
in  fact,  they  put  the  riddle  clearly:  "Guess  or  be  de- 
voured." Pasteur  did  not  guess  and  was  not  devoured. 
Therein  lies  the  interest  of  this  history. 

Near  the  silk  nursery  in  which  he  had  installed  himself, 


STUDIES  OF  1865  155 

there  were  two  cultures  of  silkworms,  two  broods  (deux 
chambrées):  the  one  finished  and  ascended  to  the 
heather,  the  other  coming  out  of  the  fourth  molt.  The 
first  had  gone  along  admirably.  The  worms  had  climbed 
up  all  at  one  time,  and  appeared  so  vigorous  that  they 
were  preparing  to  make  use  of  all  the  cocoons  for  the 
egg-laying.  The  second  had  dragged  along,  and  presented 
a  bad  appearance;  the  worms  were  languishing,  ate  little, 
and  did  not  grow.  The  sequel  proved  that  this  appear- 
ance was  not  deceptive:  the  harvest  of  cocoons  was 
almost  a  failure. 

Now,  on  examining  with  the  microscope  the  chrysalids 
and  the  moths  of  the  culture  which  had  succeeded  well, 
corpuscles  were  found  everywhere  in  them,  while  there 
were  corpuscles  only  exceptionally  in  the  worms  of  the 
bad  brood.  And  this  was  not  an  exceptional  fact,  for, 
by  searching  in  the  neighborhood,  Pasteur  found  a  mul- 
tiplicity of  similar  cases. 

What  did  this  mean?  The  corpuscles  and  the  disease 
of  silkworms  were,  therefore,  two  distinct  things.  Could 
worms  be  very  healthy  and  behave  properly,  like  the 
worms  of  the  first  culture,  and  nevertheless  give  cor- 
puscular chrysalids?  Could  they  be  sick,  like  the  worms 
of  the  second,  and  not  contain  corpuscles?  To-day  we 
know  that  if  Pasteur  did  not  find  out  this  it  was  because 
he  investigated  badly,  confounding  in  his  inexperience 
two  diseases.  There  is  one  in  which  the  corpuscle  plays 
a  rôle,  another  in  which  it  does  not.  But  Pasteur  did 
not  know  this,  having  only  discovered  it  later.  And,  in' 
the  meantime,  the  disturbing  and  imperious  question 
confronted  him  :  what  conclusion  is  to  be  drawn  from  the 
preceding  observation? 

In  order  to  decide,  it  was  prudent  to  wait  and  see  what 
would  become  of  the  cocoons  of  the  bad  brood.  In  fact, 
in  studying  them  day  by  day,  as  they  developed,  Pasteur 


156  pasteur:  the  history  of  a  mind 

saw  that  the  number  of  those  containing  corpuscles 
increased  more  and  more.  Among  the  worms,  the  cor- 
puscles were  rare.  In  the  chrysalids,  especially  in  the 
older  ones,  the  corpuscles  were  frequent.  Finally,  not  a 
single  one  of  the  moths  was  free  from  them,  and  they 
were  there  in  profusion. 

The  question  seemed,  therefore,  to  be  cleared  up,  for 
how  could  one  interpret  this  double  observation  other- 
wise than  by  saying  :  there  is  a  disease  which  can  weaken 
the  worm  in  the  absence  of  the  corpuscle,  but  of  which 
the  corpuscle  is  the  tardy  evidence.  The  two  broods 
have  suffered  from  this  disease  but  the  first  has  been 
attacked  only  when  the  worms  were  near  the  cocoon 
stage,  and  this  brood  has  succeeded  well  although  it 
has  been  a  little  diseased.  In  the  second,  the  disease 
has  attacked  the  worms  more  severely,  and  it  is  for  this 
reason  that  this  brood  has  been  languishing  and  has 
almost  miscarried. 

This  interpretation,  we  know  to-day,  is  inexact,  and, 
consequently,  it  was  perilous.  Its  danger  was  that  it 
led  to  a  practical  conclusion  which  Pasteur  did  not  hesi- 
tate to  draw.  From  the  moment  that  the  corpuscle 
appeared  thus  as  the  evidence  of  an  advanced  disease, 
it  is  clear  that  it  would  be  more  advantageous  to  obtain 
eggs  from  the  non-corpuscular  moths  rather  than  from 
the  corpuscular  moths.  The  first  might  be  diseased,  but 
they  would  have  been  so  for  a  shorter  period  and  prob- 
ably less  seriously.  "To  say  that  the  disease  should 
be  regarded  as  affecting  by  preference  the  chrysalid  and 
the  moth  is  only  to  say  that  at  this  age  it  manifests  itself 
more  apparently  and  also  without  doubt  more  danger- 
ously for  its  posterity."  It  is  thus  that  Pasteur,  starting 
from  a  false  idea,  immediately  put  the  capstone  upon  a 
method  of  egg-selection  which  became  theoretically  and 
practically,  still  better  when  the  false  idea  which  had 


STUDIES  OF  1865  157 

inspired  it  was  replaced  by  a  true  idea.  For  the  cor- 
puscle becoming,  as  it  is  really,  the  sole  cause  and  not 
simply  the  effect,  or  the  witness,  of  the  disease,  its  elimi- 
nation was  all  the  more  profitable,  and  it  is  thus  that 
error  sometimes  leads  to  the  truth.  But  let  us  not  trust 
too  much  to  this  example. 

However  this  may  be,  Pasteur  found  himself  led  by 
his  manner  of  seeing  things,  to  the  same  method  of 
egg-selection  as  Osimo,  and  it  is  curious  to  note  with 
what  firmness,  after  15  days  only  of  sojourn  in  the  places, 
he  indicates  to  the  Agricultural  Committee  of  Alais,1 
the  26th  of  June,  1865,  and  repeats  the  25th  of  September 
following,  before  the  Academy,  the  conditions  of  a  good 
method  of  egg-selection.  "This  means  will  consist  in 
isolating,  at  the  moment  of  egg-laying,  each  couple, 
male  and  female.  After  the  mating,  the  female,  set 
apart,  will  lay  her  eggs;  then  one  will  open  her,  as  well 
as  the  male,  in  order  to  search  therein  for  the  corpuscles. 
If  they  are  absent  both  from  male  and  female,  he  will 
number  this  laying  which  shall  be  preserved  as  eggs 
absolutely  pure,  and  bred  the  following  year  with  par- 
ticular care.  There  will  be  eggs  diseased  in  various 
degrees  according  to  the  greater  or  less  abundance  of 
the  corpuscles  in  the  male  and  female  individuals  which 
have  furnished  them."2 

It  is,  on  the  whole,  a  return  to  the  procedure  of  Osimo, 
tried  and  judged  worthless  by  Cantoni,  as  we  have  just 
said.  Why  had  it  miscarried  when  it  ought  to  have 
succeeded?  Perhaps  because  it  had  not  been  tried  with 
confidence,  with  the  necessary  faith,  perhaps  because 
Cantoni  had  not  sufficiently  protected  his  worms  from  a 
new  contagion,  the  effects  of  which  he  had  confounded 
with  those  of  heredity.     When  one  follows  an  idea  in 

1  Études  sur  la  maladie  des  vers  à  soie,  t  II.  p.  159. 

2  Comptes  rendus  de  l'Académie  des  Sciences,  t.  LXI,  25  Sept.  1865. 


158  pasteur:  the  history  of  a  mind 

the  air  he  must  indeed  go  haphazard,  and  the  least 
check  discourages.  The  idea  of  Pasteur  had,  on  the 
contrary,  an  experimental  foundation,  and  any  one 
could  trust  him  when  he  followed  an  idea  proceeding 
from  experiment.  Ordinarily  he  distinguished  very 
quickly  whether  a  thing  was  true  or  false. 


IV 

STUDIES  OF  1866 


However,  in  the  subject  under  consideration,  Pasteur 
continued  to  deceive  himself  during  the  whole  of  the 
year  1866,  in  consequence  of  a  defect  of  technique  which 
we  must  notice.  He  had  had  at  heart  to  apply  himself 
his  method  of  egg-selection  in  order  to  procure  mate- 
rials for  study  the  following  year.  He  had,  therefore, 
sought  in  the  vicinity  of  Alais  chrysalids  and  moths 
as  healthy  as  possible.  But  the  country  was  thoroughly 
infected;  moreover,  the  cultures  were  far  advanced  in 
that  place,  and  for  the  greater  part  had  been  used  for 
the  spinning.  It  was  with  great  difficulty  that  he  could 
procure  a  few  cocoons  derived  from  a  culture  in  appear- 
ance quite  healthy  and  successfully  completed.  He 
brought  them  to  Paris  to  obtain  their  eggs. 

In  the  passage  which  I  have  just  transcribed,  Pas- 
teur says  that  one  opens  the  male  and  female  to  seek 
therein  the  corpuscles.  They  proceeded  at  that  time  by 
removing  with  scissors  a  part  of  the  skin  of  the  abdomen: 
they  spread  out  this  shred  upon  a  glass  slide,  scraped  off 
a  little  of  the  adipose  cellular  tissue  which  was  brought 
away  with  it,  and  examined  this  fragment  after  having 
compressed  it  under  a  cover-glass.  It  was  only  later 
that  the  moth  was  ground  up  in  a  mortar  to  study  a 
drop   of  the  pap  under  the  microscope.     This  slight 


STUDIES  OF  1866  159 

detail  has  a  very  great  significance.     The  second  process 
is  the  only  reasonably  safe  one. 

On  the  contrary,  the  first  method  is  liable  frequently 
to  overlook  the  presence  of  the  corpuscles,  and  we  shall 
see  here  how  things  go  on  in  a  research.  The  method 
then  adopted  by  Pasteur  was  the  result  of  his  false 
idea.  If  Pasteur  had  considered  these  corpuscles  as 
parasites,  he  surely  would  have  concluded  that  they 
might  be  in  one  place  and  not  in  another,  and  that  it 
would  be  necessary  to  seek  them  in  various  places.  But 
he  was  convinced  that  the  corpuscle,  being  a  tardy  sign 
of  the  pre-existing  disease,  was  a  product  of  transforma- 
tion, or,  to  employ  a  medical  expression,  a  product  of 
retrogression  of  the  cells  of  the  tissues.  Now,  following 
this  hypothesis,  it  should  occur  everywhere  in  the  body. 

The  method  of  research,  imperfect  because  it  had  been 
born  of  a  false  idea,  deceived  Pasteur  and  plunged  him 
deeper  into  his  idea.  In  the  eight  couples  brought 
from  Alais  and  which  he  had  studied  in  Paris,  he  be- 
lieved he  had  found  one  in  which  the  male  presented  a 
few  corpuscles,  and  the  female  not  any.  As  a  matter  of 
fact,  she  also  contained  them,  as  shown  by  the  result  of 
the  cultures  in  which  a  few  corpuscles  appeared,  not  in 
the  worms  and  the  chrysalids  coming  from  these  eggs 
but  in  the  moths.  This  phenomenon,  spontaneous  in 
appearance,  of  corpuscles  in  a  culture  which  it  seemed 
ought  to  be  exempt,  naturally  confirmed  Pasteur  in  his 
belief  in  the  internal  origin  of  the  corpuscle.  It  is  thus 
that  a  mode  of  examination  inspired  by  a  false  idea  leads 
sometimes  to  the  confirmation  of  this  false  idea,  and  it  is 
thus  moreover  that,  during  the  whole  of  the  campaign 
of  1866,  Pasteur  persisted  in  likening  the  corpuscle  to 
pus-globules  and  even  to  red  blood-globules.  He  came 
back  definitely  to  the  idea  of  parasitism  only  after  an 
experiment  of  Gernez  which  we  shall  find  in  its  place. 


160  pasteur:  the  history  of  a  mind 

On  the  whole,  at  this  time,  any  one  who  judged  super- 
ficially would  have  concluded  that  Pasteur  brought  for- 
ward nothing  new.  He  shared  the  errror  of  Philippi, 
of  Vittadini,  and  of  Cornalia,  upon  the  origin  of  the  cor- 
puscle: his  method  of  egg-selection,  proposed  by  Osimo, 
and  then  by  Cornalia,  had  miscarried  in  the  hands  of 
Cantoni  and  of  Bellotti.  It  is  necessary  to  look  at  the 
subject  closely  to  see  that  Pasteur  brought  into  this 
study  another  idea  than  his  predecessors.  This  idea 
was  that  of  undertaking  comparative  cultural  experi- 
ments upon  healthy  eggs  and  diseased  eggs.  The 
method  of  egg-selection  which  he  recommended,  how- 
ever mediocre  it  might  be  from  the  theoretical  point  of 
view,  however  bad  it  might  be  from  the  industrial 
point  of  view,  judging  from  the  results  of  Cantoni,  was, 
however,  sufficient  to  maintain  those  original  differences 
between  the  eggs,  the  influence  of  which  it  was  important 
to  examine.  "The  process  of  selection  to  which  my 
first  researches  had  led  me  seemed  to  me,  "  says  Pasteur,1 
"to  have  an  importance  more  scientific  than  industrial.' ' 
It  turned  out  that  this  process  contained  the  industrial 
solution  of  the  problem,  but  if  it  had  not  contained  it, 
it  would  have  led  to  it,  for  Pasteur  introduced  experi- 
ment into  a  question  where  there  had  been  hitherto 
only  empiricism. 

His  plan  of  campaign  for  the  cultures  of  1866  was, 
therefore,  already  outlined.  After  having  obtained  the 
eggs  from  his  different  pairs  of  moths  which  were  more 
or  less  corpuscular,  he  would  first  try  these  out  ahead 
of  the  main  brood,  which  is  done  in  March  and  April  in 
small  lots  upon  leaves  of  the  mulberry  cultivated  in 
hothouses,  then  in  the  big  cultures  of  May  and  June. 
Made  with  the  same  precautions  and  under  the  same 
conditions,  the  culture  of  these  eggs  of  different  origin 

1  Études  sur  la  maladie  des  vers  à  soie,  t.  I,  p.  55. 


STUDIES  OF  1866  161 

ought  to  give,  as  regards  the  influence  of  the  corpuscles 
of  the  father  and  of  the  mother  upon  the  result  of  the 
industrial  culture,  or  of  the  culture  for  eggs,  information 
which  could  not  fail  to  be  very  important,  whatever 
might  be  the  true  significance  of  the  corpuscle  itself. 
In  fact,  advancing  with  this  light,  Pasteur  perceived 
immediately  a  certain  number  of  facts  of  the  greatest 
importance. 

The  first  fact  was  that  on  a  large  scale  in  the  industrial 
culture  the  batches  of  eggs  behaved  worse  and  worse, 
that  is  gave  less  and  less  cocoons,  in  proportion  as  the 
parents  were  more  and  more  occupied  by  corpuscles. 
This  sufficed  to  establish  between  the  existence  or  the 
number  of  the  corpuscles  and  the  presence  of  the  disease, 
the  bond  of  union  which  was  the  first  need  of  the  new 
method. 

The  second  fact  was  that  eggs  laid  by  corpuscular 

moths  were  not,  per  se,  destined  to  miscarry,  and  might 

develop  good  cocoons  giving  acceptable  yields.     Such 

was,   for  example,  the  case  of  the  eggs  received  from 

Japan,  which,  although  corpuscular,  were  nevertheless 

much  sought  after  by  silk-growers.     This  robust  race 

seemed  better  to  resist  the  prevalent  disease.     Such  was 

also  the  case  for  several  cultures  of  French  races.     But 

none  of  these  cultures,  even  those  which  had  yielded  the 

greatest    number   of    cocoons,    could    give   good   eggs, 

because  all  the  moths  were  strongly  corpuscular.     This 

explained  why  one  sometimes  miscarried  in  selecting 

eggs  derived  from  a  successful  culture.     The  success 

of  this  culture  proved  nothing  as  to  the  egg.     In  addition, 

control  by  means   of   the   microscope   was   necessary. 

And  so  one  came  back  to  the  method  of  egg-selection, 

authoritatively    recommended    by  Pasteur,   this  being 

brought   forward   once   more,    singularly   strengthened 

by  its  first  trial. 
11 


162  pasteur:  the  history  of  a  mind 

Finally,  another  prime  fact  was  that  even  in  the  most 
corpuscular  broods,  where  the  mortality  of  the  worms 
or  of  the  chrysalids  had  been  the  greatest,  one  always 
found  some  non-corpuscular  moths  that  would  give  better 
eggs  than  those  from  which  they  themselves  had  come. 
From  a  practical  standpoint  this  was  of  the  highest 
importance.  Among  the  objections  made  to  Pasteur, 
from  the  beginning,  the  following  had  actually  figured: 
If  the  disease  is  indeed  characterized  by  the  presence 
of  an  abundance  of  the  corpuscles,  as  you  say  it  is,  and 
as  you  prove  it  to  be,  it  is  then  widespread,  universal, 
and,  this  being  so,  how  shall  we  proceed  to  find  the  neces- 
sary eggs,  we  do  not  say  for  the  regeneration,  but  for 
the  simple  conservation  of  the  French  and  Italian  races, 
very  superior  from  the  point  of  view  of  yield  and  of  the 
quality  of  the  silk  to  the  Japanese  races,  which  are 
replacing  them  little  by  little  in  all  the  silk-growing 
lands.  To  this  Pasteur  could  reply:  But  here  are  co- 
coons of  a  French  race  which  I  have  just  brought  from 
one  of  the  most  infected  districts  !  Look  at  them,  study 
them  under  the  microscope,  and  you  will  see  that  they 
promise  results  still  more  beautiful  for  next  year.  Do, 
therefore,  as  I  do  :  let  each  one  procure  eggs  for  himself, 
as  I  do  for  myself.  If  you  tell  me  that  the  microscope 
frightens  you,  and  that  its  manipulation  seems  to  you 
not  easy,  I  reply  that  there  is  in  my  laboratory  a  little 
girl  eight  years  old  who  knows  how  to  do  it  very  well. 


V 
IS  THE  CORPUSCLE  THE  CAUSE  OF  THE  DISEASE? 

But  this  apparent  disappearance  of  corpuscles  in  some 
of  the  moths  descended  from  a  corpuscular  pair  had  theo- 
retical consequences  more  far-reaching  than  its  practical 


IS  THE  CORPUSCLE  THE  CAUSE  OF  THE  DISEASE?    163 

consequences.  What  signified  these  healthy  individuals 
in  a  progeny  strongly  infected  from  both  parents,  and 
evidently  attacked  by  a  hereditary  taint?  "Can  it  be 
that  among  the  eggs  of  a  laying,  derived  from  a  male 
and  a  female  badly  diseased,  there  are  some  healthy 
eggs?  Or  will  some  eggs  slightly  diseased  give  worms 
which  recover  health  during  the  culture?  I  do  not 
know  which  of  these  two  interpretations  is  the  better, 
and  both  are  perhaps  correct."1  The  phrase  is  curious, 
and  bears  witness  that  Pasteur  began  to  doubt  in  1866 
concerning  the  interpretation  of  the  phenomena  which 
he  had  accepted  hitherto.  The  idea  of  a  constitutional 
disease  of  which  corpuscles  were  only  the  external  and 
later  sign  did  not  harmonize  very  well  with  this  presence 
of  a  few  healthy  eggs  in  the  midst  of  their  diseased 
neighbors.  Excluding  parasitism,  one  does  not  com- 
prehend this  immunity  of  some  individuals  in  the  midst 
of  others  entirely  alike  in  that  they  are  the  descend- 
ants of  the  same  organism.  But  this  idea  of 
parasitism,  which  was  blended  with  the  idea  of  the  cor- 
puscle as  a  cause  of  the  disease,  was  repulsed  by  Pasteur 
at  this  moment  with  a  kind  of  obstinacy,  and  with  such 
a  singular  mixture  of  true  and  false  arguments  that  it  is 
useful  to  pass  them  in  review.  To  do  so  will  be  to  study 
him  in  a  vital  point  of  his  career,  that  in  which  he  aban- 
dons tradition  and  launches  out  into  new  ways. 

He  enumerated  these  arguments  himself  the  following 
year,  for  his  scruples  were  of  long  duration.  "Is  the 
disease  parasitical?"2  he  asks  himself  in  the  note  pre- 
sented to  the  Imperial  Commission  of  Silk  Culture,  in  its 
sitting  of  January  12,  1867,  and  he  rejects  this  opinion 
for  the  following  reasons  : 

1.  "Because  the  disease  is  certainly  constitutional  in 

1  Études  sur  la  maladie  des  vers  à  soie,  t.  II,  p.  165. 

2  Études  sur  la  maladie  des  vers  à  soie,  t.  II,  p.  181. 


164  pasteur:  the  history  of  a  mind 

a  great  number  of  circumstances,  and  precedes  the  ap- 
pearance of  the  corpuscles."  We  recognize  there  the 
influence  already  noted  by  us  of  that  preliminary  ob- 
servation on  a  culture  which  behaved  badly  although 
the  worms  did  not  contain  corpuscles.  We  know  to-day 
that  Pasteur  had  fallen  by  chance  upon  a  culture  at- 
tacked by  another  disease  than  pébrine,  the  disease  of 
morts-flats.1  Pasteur,  who,  at  this  moment,  spoke  only 
of  the  disease  of  silkworms,  had  confounded  everything 
and  could  believe  in  a  disease  of  corpuscles  without 
corpuscles; 

2.  "  Because  the  feeding  of  corpuscular  substances 
often  kills  the  worms  without  giving  them  corpuscles." 
Here  again,  there  was  an  error  of  interpretation,  due  to 
the  same  reasons  as  the  above.  Pasteur  had  very  clearly 
perceived  that  the  criterion  of  the  corpuscle  as  cause, 
and  of  the  corpuscle  as  effect  and  evidence  of  the  disease, 
was  an  inoculation  experiment.  If  it  had  been  possible 
to  give  the  corpuscular  disease  to  healthy  worms  by 
causing  them  to  feed  upon  corpuscles  derived  from  a 
preceding  silkworm  culture,  one  would  have  singularly 
enlightened  not  only  the  etiology  of  the  disease,  but  also 
the  causes  of  its  vitality  and  of  its  propagation,  of  its 
endemic  and  epidemic  character.  With  Pasteur  the  ex- 
ecution followed  close  upon  the  idea,  and  the  experiment 
was  made.  He  had  taken,  in  1866,  as  infectious  matter, 
very  corpuscular  dirt  scraped  up  in  a  culture  chamber, 
and  the  mashed  substance  of  a  very  corpuscular  moth 
or  worm.  The  worms  to  which  he  had  fed  the  leaves 
of  the  mulberry,  thus  infected,  had  showed  at  the  end 
of  some  days  a  considerable  mortality  which  Pasteur 
had  the  right  to  attribute  to  the  infected  food  and  to 
the  prevailing  disease  :  in  reality  it  again  resulted  from 
the  intervention  of  the  disease  of  the  morts-flats.     But 

1  Flacherie.  TVs. 


IS  THE  CORPUSCLE  THE  CAUSE  OF  THE  DISEASE?     165 

seeing  worms  inoculated  with  corpuscular  materials  die 
rapidly  and  yet  not  contain  corpuscles,  we  still  under- 
stand how  Pasteur  may  have  been  able  to  believe  that 
the  corpuscles  not  only  were  not  the  cause  of  the  disease, 
but  were  not  even  the  constant  sign  of  the  disease,  and 
could  be  absent  when  the  disease  was  in  too  rapid  evolu- 
tion, for  example  when  the  substance  relied  upon  to  pro- 
duce it  had  too  active  toxic  qualities  and  killed  the 
worm  too  quickly,  as  was  apparently  the  case  in  these 
two  experiments; 

3.  "I  have  not  been  able,"  continues  Pasteur,  "to 
discover  up  to  the  present  time  a  mode  of  reproduction 
of  the  corpuscle,  and  its  manner  of  appearance  makes 
it  resemble  a  product  of  the  transformation  of  the  tis- 
sues." Here  Pasteur  paid  the  penalty  of  his  inexperi- 
ence in  the  world  of  beings  to  which  the  corpuscle  be- 
longs, a  world  where  the  forms  of  reproduction  are  quite 
other  than  in  the  world  of  microbes,  which  he  knew  the 
best.  Without  entering  into  details,  we  must  know  that 
the  corpuscle,  instead  of  increasing  by  segmentation  or 
by  budding  as  do  the  bacilli  or  the  yeasts,  can,  under 
certain  circumstances,  swell  up  into  a  voluminous  proto- 
plasmic mass  with  almost  invisible  contours.  This  in- 
sinuates itself  into  the  tissues,  penetrates  them  with  an 
almost  invisible  network  in  which  then  only  begins  the 
process  of  delimitation  which  divides  it  into  distinct 
and  sharply  contoured  corpuscles.  From  the  initial  cor- 
puscle we  have  come  to  some  thousands  of  identical 
corpuscles,  children  of  the  same  father.  Pasteur  had 
indeed  seen  this  phenomenon  of  the  organization  of  a 
sort  of  amorphous  matrix.  He  described  it  with  a 
marvelous  precision  because  he  was  a  master  observer. 
He  pointed  it  out  to  his  draftsman,  Lackerbauer,  who 
strove  to  represent  it  in  two  plates  (pp.  28  and  64).  But 
he  does  not  know  how  to  interpret  it,  and,  as  he  sees 


166  pasteur:  the  history  of  a  mind 

the  corpuscle  appear  in  the  midst  of  all  the  tissues  of  the 
diseased  worm,  he  is  confirmed  naturally  in  his  idea 
that  the  disease  is  constitutional  and  that  the  corpuscle 
indicates  only  one  of  the  stages  of  it,  that  in  which  it 
becomes  apparent  under  the  microscope. 

It  is  a  singular  thing,  that  while  his  spirit  marched  in 
these  pathways  and  would  not  be  turned  aside,  his 
assistants  (préparateurs),  to  whom  he  said  nothing  of 
what  he  thought,  were  persuaded  that  he  was  firmly 
attached  to  the  idea  of  the  corpuscle  as  a  cause.  They 
were  astonished  that  he  did  not  make  the  crucial  experi- 
ment, and  endeavor  to  give  to  healthy  worms  by  means 
of  corpuscular  food,  not  the  disease  with  a  rapid  evolution 
of  which  we  have  just  spoken  and  which  did  not  re- 
semble the  corpuscular  disease,  but  that  same  disease 
with  its  slow  evolution  and  concomitant  developmen  of 
the  parasites.  Relying  on  the  interpretation  he  had 
given  to  his  first  experiment,  Pasteur  did  not  hasten  to 
begin  a  second.  When  that  appeared  useful  to  him  it 
was  too  late.  He  was  in  Paris.  His  associate,  M. 
Péligot,  could,  nevertheless,  give  him  some  worms  of  a 
culture  which  was  delayed.  With  these  the  inoculation 
gave  results  quite  other  than  at  Alais;  the  worms  had  not, 
apparently,  suffered  from  the  contaminated  food,  and 
Pasteur  was  very  much  embarrassed  until  he  learned 
that  Gernez  had  at  Valenciennes  semi-annual  Japanese 
"graine,"  that  is  to  say,  eggs  which  would  hatch  the  same 
year  they  were  laid,  and  give  a  second  culture  of  worms. 
Moreover,  these  eggs  were  healthy,  the  parents  not  being 
corpuscular.  He,  therefore,  asked  Gernez  to  do  over  the 
experiment  which  had  been  made  at  Alais  with  worms  ob- 
tained from  Péligot,  and  observe  whether  the  difference 
in  results  obtained  in  Gard  and  in  Paris  was  not  related  to 
the  age  at  which  the  worms  had  been  subjected  to  the 
contagion  of  the  disease.     For  him  it  was  always  the 


IS  THE  CORPUSCLE  THE  CAUSE  OF  THE  DISEASE?     167 

question  of  seeking  the  relation  which  existed  between 
the  time  of  the  corpuscular  feeding  and  the  development 
of  the  disease  with  or  without  corpuscles.  For  Gernez, 
who  believed  Pasteur  converted  to  the  idea  of  the  cor- 
puscle as  cause,  the  question  was  simpler:  the  only- 
question  was  to  know  whether  the  inoculated  worms 
would  have  corpuscles,  and  the  healthy  worms  would  not 
have  them.  From  this  point  of  view,  his  experiment  was 
particularly  convincing.     Of  four  lots  of  40  worms  each  : 

The  first,  fed  with  ordinary  leaves,  gave  27  healthy 
cocoons; 

The  second,  fed  with  leaves  moistened  with  ordinary 
water,  gave  19  cocoons  of  which  not  one  was  corpuscular; 

The  third,  fed  after  the  third  molting  with  leaves 
moistened  with  water  containing  the  débris  of  corpuscu- 
lar moths,  gave  only  four  cocoons  which  were  very 
corpuscular. 

The  fourth  lot,  in  which  the  feeding  of  corpuscular 
leaves  had  commenced  only  after  the  fourth  molt,  gave 
22  cocoons,  all  or  almost  all  corpuscular. 

Here  we  behold  a  spectacle  rare  in  the  life  of  Pasteur: 
an  experiment  the  full  and  complete  meaning  of  which 
he  does  not  immediately  comprehend.  This  experiment 
was  highly  pertinent.  It  realized  as  in  a  synthesis  the 
principal  aspects  of  the  disease.  The  third  lot  was  an 
example  of  those  silkworm  cultures  which,  after  having 
begun  well,  perish  by  the  way  and  do  not  reach  the  cocoon 
stage.  The  fourth  lot  was  an  example  of  those  cultures 
which  succeed  well  but  are  incapable  of  furnishing  good 
eggs.  The  first  and  the  second  lot  bore  witness  to  the 
worth,  when  it  is  not  infected,  of  a  "graine"  resulting 
from  egg-selection  under  the  microscope,  made  upon  a 
diseased  culture.  All  that  spoke  at  the  same  time  in 
favor  of  Pasteur's  method  and  of  the  corpuscle  as  a 
cause,  but  Gernez,  who  believed  his  master  converted 


168  pasteur:  the  history  of  a  mind 

to  this  doctrine,  was  somewhat  astonished  that  Pasteur 
saw  in  his  experiment  only  the  practical  side,  and  did 
not  flash  everywhere  the  light  which  shone  out  of  it. 
In  reality,  Pasteur  had  not  seen  it.  The  proof  is  that 
this  experiment  was  announced  to  the  Academy  by  him 
the  26th  day  of  November,  1866,  and  that  in  January, 
1867,  he  was  still  asking  himself  whether  the  disease 
was  parasitic,  and  was  still  advancing  against  this  idea 
the  arguments  which  we  have  just  examined.  He 
changed  his  opinion  on  this  subject  only  during  the 
course  of  the  year  1867,  and  this  change  of  front  has 
made  that  the  decisive  year.  He  had  until  then  marched 
directly  toward  the  promised  land,  but  he  had  marched 
backwards.  As  soon  as  he  turned  about,  the  whole  of 
his  conquest  appeared  to  him  at  once. 


VI 

STUDIES  OF  1867 


He  began  in  fact  the  early  experiments  of  1867  with 
clarified  ideas,  and  also,  which  was  not  less  important, 
with  means  for  work  and  experiment.  The  eggs  which 
he  had  prepared  in  1865  and  which  had  served  for  his 
experiments  of  1866  were  not,  as  we  have  seen,  wholly 
freed  from  corpuscles.  By  raising  them  under  special 
conditions  of  cleanliness,  by  giving  to  his  worms  space 
so  that  they  would  not  infect  each  other,  by  isolating  the 
divers  lots  in  separate  baskets,  by  shiftings,  that  is  to 
say  by  removing  the  broods  into  the  open  air,  all  prac- 
tices which,  in  his  mind,  were  so  many  hygienic  measures 
as  well  as  precautions  against  contagion,  he  had  suc- 
ceeded in  having  in  1866  a  great  number  at  least,  if 
not  whole  lots,  of  moths  which  were  non-corpuscular. 


STUDIES  OF  1867  169 

giving  with  certainty  eggs  that  Pasteur  was  content 
to  call  healthy,  but  which  to-day  we  would  say  were  free 
from  parasites.  It  was  with  these  eggs,  the  hereditary 
conditions  of  which  he  knew,  that  he  began  the  tentative 
experiments  and  the  large  cultures  of  1867. 

The  first  thing  which  he  had  to  ask  himself,  since  he 
had  not  yet  renounced  the  idea  of  a  constitutional 
disease  existing  before  the  appearance  of  the  corpuscles, 
was  whether  the  districts  of  silk  husbandry  truly  consti- 
tuted, as  was  said  over  and  over,  a  deleterious  center, 
an  infected  district,  in  which  the  disease  and  the  cor- 
puscle would  appear  inevitably,  carried  by  the  ambi- 
ent air  into  the  healthiest  broods.  This  doctrine  spoke 
too  much  in  favor  of  inaction  and  indolence,  not  to  have 
many  partisans. 

To  this  objection  Pasteur  was  able  to  respond  at  the 
end  of  his  preliminary  experiments  by  showing  some 
lots  of  worms,  offspring  of  non-corpuscular  parents  that 
had  passed  through  the  entire  metamorphosis  without 
being  attacked,  and  had  produced  eggs  which  in  turn 
were  free  from  corpuscles,  and  this  too,  although  they 
were  raised  not  only  in  an  infected  district,  but  in  a 
silkworm  nursery  where  by  the  side  of  them,  other  lots 
died  from  the  disease.  Not  only  did  the  sound  worms 
remain  sound,  but  their  general  health  seemed  to  be 
improved,  and  from  1865  to  1866,  from  1866  to  1867, 
one  saw  the  broods  improve  just  in  proportion  to  the 
original  purity  of  the  eggs. 

Assured  now  of  not  seeing  the  corpuscles  appear  in  these 
sound  lots,  one  could  perform  experiments  on  corpuscular 
contagion,  beginning  it  at  different  ages,  could  repeat 
on  a  large  scale  the  experiment  of  Gernez,  and  could 
synthesize  the  results.  This  synthesis  is  most  clear, 
and  we  may  summarize  it  very  simply. 

If  we  take  sound  worms  and  make  them  swallow  or 


170  pasteur:  the  history  of  a  mind 

by  puncture  inoculate  them  with  fresh  corpuscles  taken 
either  from  a  diseased  worm,  or  from  its  excretions, 
the  worms  thus  treated  are  sure  to  be  attacked  with  a 
disease  which,  in  its  external  characters,  recalls  com- 
pletely pébrine,  and  correlatively,  the  corpuscles  thus 
introduced  into  their  organism,  develop  there  until  they 
have  invaded  it  throughout.  The  corpuscle  is,  therefore, 
the  cause  of  the  disease,  and  pébrine  is  due,  and  due 
solely,  to  the  abnormal  development  of  these  little 
organisms.  All  uncertainty  has  disappeared,  and 
Pasteur  adopts  anew  the  doctrine  of  the  corpuscle  as 
cause,  and  the  parasitic  theory. 

Fortunately,  the  progress  of  the  disease  is  not  as  rapid 
as  it  is  certain.  It  is  nearly  30  days  after  infection  be- 
fore the  animal  is  sufficiently  invaded  by  the  parasite 
to  be  truly  sick,  and  to  be  able  no  longer,  for  example, 
to  spin  its  cocoon.  As  its  life  in  the  larval  state  is  only 
about  35  days  long,  every  worm  which  comes  from  a 
sound  egg,  that  is  to  say  which  does  not  contain  at 
the  moment  of  its  birth  corpuscles  in  process  of  devel- 
opment, will  almost  surely  produce  its  cocoon.  In  order 
that  it  should  be  otherwise  the  larva  must  become  dis- 
eased in  the  first  days  of  its  existence,  at  a  time  when 
the  malady  is  still,  so  to  speak,  latent  in  its  neighbors, 
even  in  the  most  infected  ones,  and  when  there  are  a 
thousand  chances  that  it  will  not  come  into  contact 
with  any  mature  corpuscles  which  it  could  swallow  or 
with  which  it  could  be  infected  through  wounds. 
Therefore,  if  an  egg  is  sound,  that  is  to  say,  free  from 
corpuscles,  the  offspring  cannot  die  from  pébrine.  Here 
evidently  we  have  a  fact  of  capital  importance,  and 
it  is  not  the  only  one  of  this  order. 

There  results,  in  reality,  from  this  long  period  of 
incubation  of  the  disease,  another  consequence:  that  is 
that  the  silkworm,  passing  from  15  to  20  days  in  its 


STUDIES  OF  1867  171 

cocoon,  if  it  is  ever  so  little  diseased  at  the  beginning  of 
this  period,  and  it  may  be  so  slightly  as  to  appear  per- 
fectly sound  even  under  the  microscope,  becomes  more 
and  more  diseased,  the  few  corpuscles  which  it  contains 
multiplying  little  by  little  within  it.  They  invade  all 
the  tissues  of  the  chrysalis  and  especially  those  in  the 
midst  of  which  the  eggs  are  formed.  Consequently, 
the  latter  may  include  some  of  these  corpuscles  in  their 
interior,  and  the  worms  which  are  hatched  from  them, 
corpuscular  from  their  birth,  cannot  as  we  have  seen, 
reach  the  cocoon  stage.  The  grower  will  obtain  then 
a  commercial  harvest  from  an  egg  only  when  it  is  pure, 
and  there  is  no  certainty  of  its  being  pure  unless  it  comes 
from  moths  free  from  corpuscles. 

We  are,  therefore,  now  authorized  to  say  that  the  disease 
is  contagious  and  hereditary,  but  we  must  give  to  these 
two  words,  heredity  and  contagion,  a  well-defined  sense, 
for  they  both  represent  the  introduction,  either  into  a 
sound  worm  from  its  diseased  neighbors,  or  into  an  egg 
from  a  corpuscular  female,  of  one  sole  element,  the  cor- 
puscle in  process  of  development.  Pasteur  has  even  gone 
farther,  and  by  showing  that  at  the  beginning  of  a 
silkworm  season  there  are  no  living  corpuscles  except 
those  which  are  contained  in  diseased  eggs  he  has 
connected  these  two  questions  of  contagion  and  heredity. 
All  other  corpuscles,  all,  for  example,  which  are  present  in 
such  great  abundance  in  the  dust  of  the  hatcheries,  are 
dead  and  incapable  of  reproduction.  It  is,  therefore,  the 
hereditary  corpuscles  alone  which  permit  the  malady 
to  assume  each  year  its  contagious  character,  and  it  will 
disappear  forever  on  the  day  when,  throughout  the 
entire  world,  silkgrowers  raise  only  sound  eggs. 

Such  are  the  theoretical  conclusions  of  the  experiments 
of  1867.  The  practical  conclusions  are  not  less  clear 
cut.     "Do  you  wish  to  know,"  said  Pasteur  to  the 


172  pasteur:  the  history  op  a  mind 

silk-growers,  "whether  a  lot  of  cocoons  will  give  you  sound 
eggs?  Take  a  portion  of  them  and  heat  them  so  as  to 
hasten  four  or  five  days  the  hatching  of  the  moths,  and 
see  whether  the  latter  are  corpuscular.  The  micro- 
scopical examination  of  the  moths  is  easier  and  more 
certain  than  that  of  the  eggs  because  in  them  the  cor- 
puscles are  many  times  more  abundant.  If  the  moths 
are  bad,  send  the  cocoons  to  the  spinning  mills.  On 
the  contrary,  if  you  find  that  only  a  very  limited  number 
of  individuals  are  diseased,  allow  them  to  develop: 
the  eggs  will  be  good  and  the  brood  which  you  will  have 
from  them  the  next  year  will  be  a  successful  one.  Only, 
this  brood  will  be  unfit  for  breeding  because  of  the  initial 
presence  and  multiplication  in  it  of  the  corpuscles. 
But  do  you  wish  the  brood  to  be  sound  up  to  the  very  end 
and  give  you  perfect  eggs?  Then  take  absolutely  sound 
eggs,  coming  from  absolutely  pure  parents,  and  hatch 
them  in  conditions  of  cleanliness  and  isolation,  such 
that  infection  cannot  spread  there.  But  if,  unfortu- 
nately, the  disease  should  appear  I  still  give  you  the 
means  of  making  a  selection,  and  of  separating  rigorously 
the  sound  eggs  from  the  corpuscular  ones." 

The  problem  was,  therefore,  solved,  and  the  victory 
could  be  considered  complete.  Let  us  hasten  to  say  that 
no  part  of  it  is  more  widely  discussed  at  the  present  time. 
The  examination  of  eggs  with  the  aid  of  the  microscope 
which  had  been  judged  impossible  has  become  a  custom. 
The  growers  of  silkworms  have  made  it  encircle  the  globe 
as  they  once  did  the  disease  itself,  and  pébrine  has 
ceased  to  haunt  the  mind  of  those  engaged  in  the  silk- 
worm industry.  On  one  point  only  were  the  expecta- 
tions of  Pasteur  unfulfilled.  He  hoped  that  it  would  be 
possible  to  make  the  disease  disappear.  This  was  a 
noble  ambition  and  would  have  been  a  great  example. 
Experience  has  shown  that  it  was  impossible.     This  is 


THE   DISEASE    OF   THE   MORTS-FLATS    [fLACHERIE]     173 

because  the  silkworm  is  not  the  sole  host  of  the  corpuscle, 
and  do  what  you  will  to  make  this  source  of  contagion  dis- 
appear, there  are  others  open.  In  vain  M.  Susani,  for 
example,  eliminated  for  many  kilometers  around  his 
immense  establishment  of  Rancate  in  the  Brianza  every 
corpuscular  egg  :  he  still  had  corpuscular  moths,  and  he  was 
obliged  all  his  life  to  defend  himself  every  year  against 
the  contagion  of  the  disease  which  he  had  tried  in  vain 
to  extirpate.  Man  cannot  suppress  an  epidemic  disease, 
but  he  can  keep  it  within  bounds,  and  render  it  almost 
inoffensive.  A  great  lesson,  which,  from  the  silkworm 
industry,  has  passed  into  pathology,  and  which  we  shall 
recall  later  when  we  see  Pasteur  grappling  with  human 
diseases  ! 


VII 
THE  DISEASE  OF  THE  MORTS-FLATS  [FLACHERIE]^ 

In  what  precedes,  I  have  left  out  of  consideration  all 
the  propaganda  which  Pasteur  undertook  in  order  to 
inspire  and  hasten  confidence  in  his  methods:  visits, 
correspondence,  letters  to  the  journals,  he  neglected 
nothing;  he  distributed  healthy  eggs  and  diseased  eggs, 
sought  public  judgments  on  the  results  of  the  silkworm 
cultures,  prognosticated  them  so  as  to  attract  attention 
and  stir  up  curiosity,  and  every  morning  there  was  a 
great  mass  of  letters  which  he  opened  with  emotion, 
smiling  at  the  good  news,  attentive  to  the  bad. 

In  1867,  Pasteur  had  .distributed  in  small  lots  his 
healthy  eggs  prepared  in  1866,  and  the  success,  we  knew, 
had  been  general.  However,  as  the  letters  came  in 
announcing  the  result  of  the  cultures,  we  found  our 

1  There  are  no  English  equiva^nts.  Both  words  refer  to  the  gaseous 
condition  of  the  feces,  and  mean  death  or  disease  due  to  flatulence.     Trs. 


174  pasteur:  the  history  of  a  mind 

master  more  and  more  anxious.  He  kept  us  so  remote 
from  his  thought  that  we  could  not  explain  his  uneasiness 
till  that  day  when  he  appeared  before  us  almost  in  tears, 
and,  dropping  discouraged  into  a  chair  said:  "Nothing 
is  accomplished;  there  are  two  diseases!" 

He  had  in  mind  this  disease  of  the  morts-flats,  con- 
cerning which  I  have  already  made  brief  mention. 
He  had  known  it  for  a  long  time,  indeed  since  his 
first  sojourn  in  the  South  in  1865,  where  one  of  the  two 
cultures  of  silkworms  which  served  for  the  beginning 
of  his  deductions  was  attacked  by  this  disease  at  the 
same  time  as  by  that  of  the  corpuscles.  But  the  cases 
of  association  were  so  frequent,  precisely  because  the 
disease  of  the  corpuscles  was  widespread,  that  Pasteur 
had  considered  the  two  affections  as  intimately  con- 
nected and  likely  to  disappear  together. 

During  the  silkworm  cultures  of  1866,  the  two  diseases 
were  somewhat  separated  both  in  fact  and  in  his  mind. 
He  had  sometimes  seen  the  second  appear  in  cultures 
hereditarily  exempt  from  the  first,  and  he  had  asked 
himself  whether  they  were  not  independent.  His  pub- 
lications at  this  time  bear  the  trace  of  these  preoccupa- 
tions, which  had  not  yet  become  a  source  of  uneasiness. 
The  cases  of  morts-flats  had  been  rare,  and  had  besides 
appeared  here  and  there,  without  visible  preference, 
like  cultural  accidents  attributable  to  the  growers. 

It  was  in  1867,  in  the  preliminary  trials,  and  especially 
in  the  large  cultures,  that  the  gravity  of  the  danger  first 
appeared.  Almost  entire  lots  of  eggs  free  from  cor- 
puscles and  bred  by  various  growers  had  perished 
everywhere  of  the  disease  known  as  morts-flats,  what- 
ever might  be  the  circumstances  of  place,  time,  climate 
and  culture.  It  could  not  be  any  longer  a  question  of 
accidents:  it  was  the  manifestation  of  an  inherited  dis- 
position, and  on  seeing  these  mishaps  renewed,  on  finding 


THE   DISEASE    OF   THE   MORTS-FLATS   [fLACHERIE]    175 

behind  the  disease  which  he  thought  he  had  conquered, 
another  redoubtable  disease,  and  one  about  which  he 
as  yet  knew  nothing,  we  can  understand  why  Pasteur 
experienced  and  exhibited  a  moment  of  despair.  The 
public,  to  which  one  shows  only  the  finished  work,  is 
ignorant  of  the  painful  hours  with  which  the  scientific 
man,  the  artist,  or  the  writer  has  paid  in  advance  for 
the  joy  of  his  success. 

Naturally,  we  strove  as  best  we  could  to  comfort  the 
discouraged  master.  Since  all  was  not  finished,  it  was 
not  necessary  to  conclude  that  nothing  was  accomplished, 
but  only  to  begin  over  again  if  necessary.  We  were 
young  and  we  had  confidence,  not  in  ourselves,  but  in 
him.  Well  employed  were  those  hours  in  which  we  saw 
him  struggling  with  these  difficult  questions,  ceaselessly 
on  the  hunt,  sometimes  deceived  in  his  previsions  and 
hesitating,  sometimes  triumphant  and  marching  with 
great  strides.  We  did  not  always  know  whither  he  was 
bent,  for  he  said  little;  but  we  tried  to  guess,  judging 
from  the  circumstances,  and  rectifying  our  ideas  by 
what  we  were  allowed  to  perceive  of  his  own. 

This  differentiation  between  the  two  diseases,  which 
had  now  become  evident,  was  a  first  step,  and  one  of  the 
most  important,  in  the  study  of  the  second  disease. 
Henceforth  only  what  belonged  to  each  disease  need  be 
credited  to  it.  At  the  beginning  of  his  researches,  as  we 
have  seen,  Pasteur  had  credited  to  the  corpuscular 
disease  results  due  to  the  other  disease.  Now,  the  light 
having  penetrated  into  obscure  corners,  many  difficulties 
and  apparent  contradictions  were  explained  and  even 
by  going  over  recollections  and  records  of  experiments, 
and  removing  therefrom  all  that  related  to  the  disease  of 
the  morts-flats,  a  very  considerable  volume  of  data 
bearing  upon  it,  was  obtained. 

The  most  striking  feature  in  its  history  was  its  mani- 


176  pasteur:  the  history  of  a  mind 

festly  hereditary  character.  As  we  have  said,  it  ravaged 
certain  lots  of  eggs,  which  were  sometimes  distributed 
among  a  number  of  silk-growers,  and  bred,  owing  to 
this  fact,  under  the  most  varied  conditions,  and  which, 
nevertheless,  were  attacked  at  the  same  period,  in  the 
same  age  of  the  worm,  as  if  they  had  all  brought  with 
them  a  germ  of  destruction.  Most  frequently  after  the 
fourth  molt,  during  the  period  of  voracity  called  the  "big 
gorge,"  when  the  healthy  worms  greedily  devour  the 
foliage  given  them,  the  diseased  worms  were  seen  to  be 
indifferent  to  the  provender,  crawling  over  the  leaf 
without  attacking  it,  even  avoiding  it,  and  having  the 
appearance  of  seeking  a  tranquil  corner  in  which  to  die. 
When  dead,  the  worm  sometimes  softened  and  rotted, 
but  sometimes  remained  firm  and  hard,  so  that  one  must 
touch  it  to  be  certain  it  was  dead.  At  other  times,  when 
the  disease  attacked  the  worm  more  slowly,  it  climbed 
the  heather,  but  with  difficulty,  slowly  spun  its  cocoon, 
sometimes  did  not  finish  it  but  left  it  in  the  condition  of 
skin,  and  died  without  changing  into  a  chrysalis  or.  a 
moth. 

In  recalling  the  conditions  under  which  the  production 
of  the  eggs  showing  this  hereditary  predisposition  to  the 
disease  of  the  morts-nats  had  taken  place,  Pasteur 
remembered  suddenly  that  one  of  the  cultures  had  not 
been  entirely  satisfactory  at  the  time  the  worms  climbed 
up  to  undergo  their  transformation.  The  worms  had 
climbed  up  soft,  had  dragged  themselves  at  this  time. 
Here  Pasteur  reaped  the  advantage  of  that  constant  and 
penetrating  supervision  which  he  exercised  over  every- 
thing. In  a  year,  he  had  become  an  excellent  breeder 
of  silkworms.  If  he  observed  well,  he  knew  also  how  to 
draw  conclusions,  and  immediately  he  reflected  that  the 
eggs  subject  to  this  hereditary  sensitiveness  to  the  morts- 
flats  must  have  come  from  those  apparently  successful 


THE   DISEASE    OF   THE    MORTS-FLATS    [fLACHERIE]    177 

cultures,  which  he  had  used  for  the  production  of  eggs 
because  the  worms  did  not  contain  corpuscles,  but  which 
showed,  on  climbing  up  the  heather  for  their  transforma- 
tion, that  peculiar  sluggishness  which  he  had  sometimes 
observed.  As  in  the  corpuscular  disease,  the  malady 
had  not  killed  the  progenitors,  but  was  not  the  less 
menacing  to  their  descendants. 

Forgetting  his  discouragement,  he  set  to  work  im- 
mediately upon  this  idea.  There  were  still  in  the 
neighborhood  some  silkworm  cultures  attacked  by  the 
disease  of  the  morts-flats.  He  took  the  cocoons  they 
had  yielded,  satisfied  himself  of  the  absence  of  corpus- 
cules, and  obtained  eggs  from  them.  These  eggs  were 
used  for  the  preliminary  cultures  of  the  following  year, 
and  as  early  as  the  20th  of  March,  1868,  he  was  able  to 
announce  to  Dumas  that,  out  of  the  seven  lots  thus 
selected  from  seven  distinct  cultures,  six  had  miscarried 
at  various  ages,  especially  in  the  fourth  molt,  with  the 
disease  of  the  morts-flats. 

"Consequently,  there  is  no  more  doubt,"  he  added,1 
"that  the  disease  of  the  morts-flats  can  be  hereditary 
and  attack  a  brood,  independently  of  all  conditions  as  to 
mode  of  hatching  of  the  eggs,  ventilation  of  the  brood, 
excessive  heat  or  cold  to  which  the  worms  are  exposed, 
conditions  which  without  doubt  may  occasionally  pro- 
voke this  same  disease.  Hence,  the  imperious  necessity 
of  never  using  for  the  egg-laying,  whatever  may  be  the 
external  appearance  or  the  results  of  the  microscopic 
examination  of  the  moths,  broods  which  have  shown 
from  the  fourth  molt  to  the  cocoon,  any  languishing 
worms,  or  which  have  experienced  a  noticeable  mortality 
at  this  period  of  the  culture,  due  to  the  disease  of  the 
morts-flats.  I  insist  again  on  this  advice,  and  with 
more  force  than  last  year." 

1  Études  sur  la  maladie  des  vers  à  soie,  t.  II,  p.  232. 

12 


178  pasteur:  the  history  of  a  mind 

He  felt,  however,  that  this  prescription  was  a  little 
uncertain.  What  is  a  languishing  worm?  One  must 
be  a  good  grower  of  silkworms  to  see  it,  and  there  were 
no  longer  any  such.  Several  years  of  successive  dis- 
asters had  overthrown  practices,  experiences,  and 
traditions.  He  must  find  for  the  disease  a  more  palpable 
sign,  and,  for  that  purpose,  must  study  it  in  its  origins, 
in  its  etiology. 


VIII 
STUDIES  OF  1868,  1869,  1870 

The  etiology  of  this  disease  was  the  work  of  the 
years  1868,  1869  and  1870,  an  intermittent  labor, 
interrupted  as  it  was  by  other  occupations.  The 
recommendation  Pasteur  had  made  to  eliminate  from 
the  egg-laying  everything  that  had  the  appearance  of 
flacherie  suppressed  for  the  time-being  all  grave  fears 
on  the  subject  of  this  disease,  leaving  the  corpuscular 
disease  alone  in  the  foreground.  It  was  urgent  to  prove 
to  all  the  worth  and  the  eminently  practical  character 
of  the  new  method  of  silkworm  breeding. 

In  this  work  Pasteur  showed  qualities  not  among 
those  of  which  I  have  undertaken  the  history,  because 
they  do  not  form  a  part  of  his  greatness,  and  because 
he  could  well  have  done  without  them.  But  I  must 
mention  them  because  they  complete  his  physiognomy. 
These  were  the  masterful  qualities  of  a  chief  of  industry 
who  watches  everything,  lets  no  detail  escape  him, 
wishes  to  know  everything,  to  have  a  hand  in  everything, 
and  who,  at  the  same  time,  puts  himself  in  personal 
relation  with  all  his  clientele,  asking  both  those 
who  are  content  and  those  who  are  not  the  reasons 
for  their  opinions. 


studies  of  1868,  1869,  1870  179 

He  knew  well  that  a  process  of  silkworm  breeding 
which  clashed  with  interests,  which  transformed  com- 
mercial or  industrial  practices,  could  not  make  its  way 
without  arousing  anger,  without  stirring  up  criticisms, 
the  more  bitter  because  they  were  not  disinterested. 
He  showed  himself  less  and  less  sensitive  to  these  at  acks 
the  surer  he  became  of  his  facts,  and  no  contradiction, 
even  though  it  came  from  the  Silk  Commission  of  Lyons 
ever  stirred  him  as  much  as  those  which  he  was  obliged 
to  encounter  later  in  connection  with  his  studies  on 
fermentation  or  researches  on  anthrax  and  human  rabies. 
Yet,  as  the  diffusion  of  the  method  had  become  a  practical 
question,  he  did  not  disdain  to  become  a  silkworm 
breeder,  and  he  went  voluntarily  to  preside  at  the  in- 
stallation of  his  process  in  the  nurseries  of  the  growers  in 
the  lower  Alps  or  the  Eastern  Pyrenees,  who  invoked 
his  aid. 

It  was  in  the  intervals  of  this  practical  apostolate 
that  he  returned  to  his  investigations  on  the  malady 
of  the  morts-flats,  which,  as  he  studied  it,  showed  itself 
to  be  more  complicated  than  the  corpuscular  disease 
and  more  nearly  related  to  human  diseases.  This  re- 
lation was  at  the  time  still  very  vague  in  the  mind  of 
Pasteur,  who  had  not  studied  medicine,  and  who  had, 
furthermore,  the  faculty  almost  necessary,  it  seems,  to 
men  of  his  temper,  of  isolating  themselves  in  what  they 
do,  and  of  working  so  must  the  better  the  less  they  look 
out  of  the  window.  But  as  these  studies  of  Pasteur 
had  brought  him  into  the  domain  of  pathology,  had 
led  him  to  examine  a  host  of  new  problems,  and  had  had 
clearly  a  reflex  action  on  his  later  discoveries,  perhaps 
it  is  well  to  state  the  point  which  he  had  reached  in  1878, 
after  10  years  of  study,  which  was  intermittent  and 
interrupted  by  other  pieces  of  work.  It  was  just  before, 
or  at  the  beginning  of  his  researches  on  anthrax,  and  the 


180  pasteue:  the  history  of  a  mind 

subject  had  not  ceased  to  haunt  his  mind.  In  this 
year,  1878,  there  was  held  in  Paris  a  Congress  on 
silk  husbandry,  where  the  subject  of  flacherie  was  much 
discussed,  and  where  Pasteur  often  found  himself  moved 
to  speak.  From  his  discourses  and  conversations  we 
gather  the  following  resume  of  his  ideas  on  a  question 
to  which  he  never  again  returned. 

We  have  described  the  external  signs  of  the  disease 
and  we  know  also  that  the  mortality  may  be  considerable 
within  a  few  days,  which  gives  it  a  distinctly  epidemic 
character.  One  might  call  it  the  cholera  or  the  typhoid 
of  the  silkworm.  But  these  are  only  words;  let  us 
endeavor  to  get  at  the  facts,  and  at  the  causes. 

The  simplest  examination  shows  that,  as  in  the  case 
of  typhoid  or  of  cholera,  it  is  the  digestive  organs  which 
are  diseased.  Sometimes  their  contents  are  all  foamy, 
and  in  full  process  of  fermentation.  Sometimes,  on  the 
contrary,  the  fecal  substances  are  in  compact  masses, 
hard,  and  of  the  same  aspect  from  one  end  to  the  other 
of  the  intestinal  tract,  which  seems  to  have  become  an 
inert  receptacle.  In  all  cases  there  is  nothing  resembling 
regular,  normal  digestion,  the  solid  product  of  which 
is  molded  and  separated  into  bits  by  the  muscles  of  the 
anus,  with  the  regularity  of  a  machine  for  making  Italian 
pastes. 

On  examining  microscopically  these  normal  excre- 
ments, we  find  therein  débris  of  leaves  but  no  microbes, 
or  almost  none.  There  is  not,  so  to  speak,  any  place  for 
them  in  the  powerful  mechanism  of  the  nutritive  system 
in  this  animal,  which  seems  made  only  to  eat.  It  is 
quite  otherwise  in  the.  diseased  worms.  Their  digestive 
tract  is  full  of  microbes;  these  are  bacilli,  more  or  less 
plump,  some  of  them  spore-bearing,  and  micrococci  in 
pairs  and  in  chains. 

This  being  the  state  of  affairs,  the  question  arises  at 


studies  of  1868,  1869,  1870  181 

once:  Is  the  disease  contagious?  Can  it  be  carried 
from  a  diseased  worm  to  a  sound  worm,  its  neighbor? 
It  happens  exactly  in  this  disease  that  the  excrements  are 
ordinarily  viscid  and  smear  the  leaves  which  the  worms 
eat  in  common.  If  we  imitate  this  natural  contagion  by 
making  worms  eat  leaves  smeared  with  the  excrement  of 
a  diseased  worm,  we  shall  see  them  become  sick  in  their 
turn,  as  in  the  case  of  the  corpuscular  disease.  The 
flacherie  is  therefore  contagious,  like  the  pébrine. 

But  here  is  a  difference  :  all  the  worms  which  had 
eaten  the  fresh  corpuscles  became  sick  at  nearly  the  same 
time.  The  ingested  corpuscle  undergoes  a  regular  evolu- 
tion, and  it  is  not  in  the  digestive  tract  that  it  develops. 
It  is  not  the  same  with  the  flacherie.  Its  stronghold  is 
in  the  intestine,  and  the  time  which  separates  the  moment 
of  contagion  from  that  of  death  may  vary  from  12  hours 
to  3  weeks,  and  even  more,  for  invariably  some  of 
the  worms  escape  death.  Therefore,  worms  which  re- 
semble each  other  in  regard  to  the  corpuscle,  no  longer 
do  so  when  exposed  to  the  germs  of  flacherie.  Thus  it  is 
that  Pasteur  encountered  for  the  first  time  this  question, 
then  so  new,  of  receptivity  to  germs,  differing  in  different 
individuals  of  the  same  species.    • 

He  discovered  a  second  question  just  as  new  to  him, 
although  it  was  a  little  less  so  to  science,  when  he  sought 
to  learn  whether  the  germs  of  flacherie  from  different 
sources  were  equivalent  from  the  point  of  view  of  the 
production  of  the  disease.  Some  bacilli  taken  from  an 
artificial  fermentation  of  mulberry  leaves,  for  example, 
caused  death  in  from  8  to  15  days.  If  we  inoculate 
fresh  worms  with  the  substance  taken  from  the  digestive 
tract  of  the  former,  death  follows  in  from  6  to  8  days. 
The  virus  is,  therefore,  augmented  in  intensity  as  the 
result  of  its  passage  through  the  organism. 

Finally,   the  influence  of  the  port  of  entry,   which 


182  pasteur:  the  history  of  a  mind 

Davaine  was  at  this  moment  occupied  in  studying  in 
anthrax,  was  also  apparent  to  Pasteur  through  the  com- 
parison which  he  had  made  of  the  results  of  inoculation 
by  pricks  and  by  contamination  of  the  digestive  tract. 
We  see  what  an  excellent  preparation  these  studies  on 
fiacherie  gave  him,  and  with  what  good  reason  he  ad- 
vised young  medical  students,  who  later  learned  the 
path  to  his  laboratory,  to  read  these  two  volumes  on  the 
disease  of  silkworms:  the  great  teachings  of  microbial 
pathology  are  already  found  there. 

This  is  not  all.  We  have  seen  that  the  germ  of  the 
corpuscle  is  not  common,  and  must  be  acquired  from  a 
living  worm,  or  from  one  just  dead,  in  order  to  preserve 
its  vitality.  Pasteur  even  believed,  as  we  have  seen, 
that  it  had  no  other  habitat  than  the  silkworm,  and 
that  man  could  make  pébrine  disappear  by  making  the 
production  of  sound  eggs  universal.  On  the  contrary, 
the  appearance  of  fiacherie  is  sometimes  spontaneous, 
and  may  result  from  an  accident  or  from  some  error 
during  the  breeding.  Whence,  then,  come  the  germs? 
The  germ  is  common,  replies  Pasteur.  It  suffices  to 
leave  in  a  flask,  at  summer  temperature,  a  bit  of  bruised 
mulberry-leaf,  in  order  to  see  appear  in  the  maceration 
microscopic  organisms  in  every  way  similar  to  those 
which  one  encounters  in  the  digestive  tract  of  the 
flatulent  worms,  a  canal  which,  in  fact,  seems  to  have 
become  an  inert  receptacle.  In  a  healthy  worm  the 
tract  arrests  or  prevents  all  development  of  microbes; 
in  a  flatulent  worm,  it  opens  the  way  for  the  germs  which 
the  leaf  introduces,  and,  with  approximately  the  same 
virulence,  the  germs  of  the  flasks  and  the  germs  of  the  in- 
testinal tract  behave  the  same.  That  explains  to  us  how 
the  disease  can  appear  sometimes  without  having  been 
introduced  from  a  distance,  a  thing  which  did  not  happen, 
at  least  so  Pasteur  thought,  in  the  corpuscular  disease? 


studies  of  1868,  1869,  1870  183 

The  discovery  of  the  common  character  of  the  germs 
of  flacherie  obliges  us  now  to  turn  back  and  ask  our- 
selves a  question.  Why,  if  this  germ  is  everywhere, 
does  it  not  develop  always  and  everywhere?  This  is 
clearly  a  general  question,  like  those  which  precede, 
and  may  be  asked  regarding  a  multitude  of  human 
diseases.  The  germ  of  tuberculosis  is  widely  dissemi- 
nated, we  could  say  to-day.  There  is  not  one  of 
us  who  has  not  inhaled  it.  We  are  exposed  to  it  every 
day  and  everywhere  !  Why  are  not  all  of  us  tuberculous? 
To  this  question,  not  yet  solved,  Pasteur  had  made, 
concerning  flacherie,  a  double  response. 

This  intermittent  and  localized  development  of  germs 
universally  distributed  can  take  place,  he  said,  whenever 
external  conditions,  of  which  the  grower  is  not  always 
the  master,  favor  the  multiplication  of  the  microbes,  or 
enfeeble  the  digestive  power  of  the  worm.  The  animal 
is  constantly  taking  in,  with  the  leaves  which  it  eats, 
germs  which  would  develop  in  a  flask  and  which  do  not 
develop  in  its  digestive  tract,  arrested  as  they  are  by 
physiological  influences.  But  imagine  that  they  are 
more  numerous  for  some  reason,  that  the  leaf  is  heated 
by  fermentation  before  being  served  to  the  worm;  or 
again  that  the  number  of  germs  remains  the  same,  but 
that  the  worms  have  been  weakened  by  a  stormy  period 
or  by  a  stifling  heat  when  no  air  is  in  circulation,  or  by 
the  fact  that  the  worm-nursery  is  too  warm  or  poorly 
ventilated,  or  by  the  result  of  some  other  accident,  and 
then  the  germs  take  advantage  of  the  lowered  resistance 
to  multiply  and  the  malady  breaks  out  ! 

Finally,  to  this  idea  add  the  fact  that  the  weakening 
of  the  digestive  tract  may  be  constitutional,  organic, 
may  result  from  the  fact  that  the  worms  which  were  the 
larval  ancestors  of  these  eggs,  were  themselves  sick  at 
the  time  of  their  pupation  or  before,  with  the  disease  of 


184  pasteur:  the  history  of  a  mind 

the  morts-fiats,  and  we  have  united  by  a  common  bond 
all  the  modes  of  appearance  of  the  disease,  both  that 
which  is  encountered  in  the  sporadic  state  on  sound  eggs 
exempt  from  all  hereditary  predisposition,  and  that 
which  rages  among  the  descendants  of  a  brood  where 
the  morts-flats  has  been. 

The  disease  of  the  morts-flats  is  then,  like  that  of  the 
corpuscles,  a  contagious  disease,  but  sometimes  be- 
cause its  germ  is  so  common,  it  may  become  a  disease 
which  appears  to  be  spontaneous,  sporadic  or  epidemic, 
benign  or  disastrous,  and  the  origin  of  which  a  super- 
ficial observer  might,  with  reason,  attribute  to  the  com- 
mon conditions  of  cold,  heat,  humidity,  electricity,  so 
often  invoked  by  ancient  medicine.  More  enlightened 
now,  we  can  say:  No,  these  common  influences  neither 
are  the  disease  nor  make  the  disease;  they  open  the  door 
for  it  and  give  it  scope.  In  this  case,  and  in  all  the  cases 
where  one  is  led  to  lay  on  them  the  blame,  we  find  on 
close  investigation  a  germ,  more  or  less  widespread, 
ordinarily  kept  within  bounds  by  natural  laws,  but  able 
when  conditions  change,  when  its  virulence  is  exalted, 
when  its  host  is  enfeebled,  to  invade  the  territory  which 
was  barred  to  it  up  to  that  time.  The  bacillus  of  flach- 
erie  is  always  present,  but  the  sound  worm  is  able  to 
defend  itself  on  the  side  where  it  is  threatened.  It  will 
not,  perhaps,  resist  a  wound — an  unusual  way  for  con- 
tagion; it  will  better  resist  an  introduction  into  the  di- 
gestive tract,  but  still  there  must  not  be  too  many  ba- 
cilli, nor  too  virulent  ones. 

For  the  same  reasons  the  hereditary  predisposition 
no  longer  makes  for  the  same  certainty  of  action  as  it 
does  in  pébrine.  There  it  resulted  from  the  deposition 
in  the  egg  of  a  germ  the  development  of  which  was  as- 
sured; here  there  is  no  transmission  of  the  germ.  We 
find,  it  is  true,  in  the  stomach  of  the  chrysalis  (a  stomach 


studies  op  1868,  1869,  1870  185 

atrophied  because  it  has  become  useless)  the  still  recog- 
nizable forms  of  organisms  which  were  present  in  the 
stomach  of  the  worm,   especially  of  those  organisms 
which  have  been  so  little  active  as  to  permit  the  worm 
to  continue  its  development  in  spite  of  the  weakening 
which  they  have  caused.     Among  these  is  a  small  fer- 
ment in  chains,  analogous  to  the  organism  figured  in  the 
fourth   section   of   Fig.    8,  page   70.     When  one  finds 
this  in  the  stomach  of  a  chrysalis  or  of  a  moth  he  may 
rest   assured   that   the   disease   of  the  morts-flats  was 
present  at  the  end  of  the  metamorphosis,  and  that  the 
egg  is  suspicious.     We  may  try  to  find  in  this  direc- 
tion a  criterion   of  purity  which  the  egg  itself  is  in- 
capable of  furnishing,   since  the  egg  contains  nothing. 
The  heredity  which  is  transmitted  is  not  the  inheritance 
of  a  germ;  it  is  the  inheritance  of  a  function,  a  reversed 
vaccination,  favoring  the  invasion  of  the  common  germ 
of  the  malady,  as  ordinary  vaccination  prevents  the 
invasion  of  the  specific  germ.     Such  is,  we  might  say 
to-day,  the  inheritance  of  tuberculosis.     If  the  tubercle 
organism  is  not  common,  if  it  is  incapable  of  developing 
outside   of  the  body,  a  fact  of  which  we  are  not  yet 
very  certain,  it  is  at  least  widely  distributed,  and  has  no 
need,  as  we  see  in  case  of  flacherie,  of  being  transmitted 
through  the  parents  by  heredity  in  order  to  attack  the 
offspring.     All  that  is  necessary  is  a  hereditary  feebleness 
in  the  functioning  of  the  lungs.     The  soil  prepared,  the 
seed   always   ready,    the   disease   will  always  find  the 
occasion  to  implant  itself. 

On  the  contrary,  as  in  flacherie,  there  will  be  always 
some  hereditary  predispositions  which  will  be  effaced 
owing  to  favorable  conditions. 

In  conclusion,  at  the  end  of  his  Études,  Pasteur  found 
not  only  that  he  had  solved  the  problem  which  he  had 
undertaken    on    the   regeneration  of  sériciculture,   but 


186  pasteur:  the  history  op  a  mind 

had  placed  on  an  experimental  basis  the  great  questions 
of  contagion  and  of  heredity  which  dominate  all  path- 
ology. He  was  ripe  to  attack  them,  and  to  solve  them 
wherever  he  should  meet  them,  for  his  mind  was  molded 
upon  them.  But  he  was  much  less  advanced  in  the 
the  matter  of  his  technique.  He  was,  in  1870,  in  a  posi- 
tion to  grasp  the  most  delicate  features  of  the  patholog- 
ical history  of  the  anthrax  of  animals  but  not  in  a  posi- 
tion to  approach  the  question  experimentally.  It  was 
necessary  for  him  first  to  perfect  his  equipment,  and  his 
methods  of  research.  The  guardian  spirit  which  seemed 
to  have  undertaken  the  direction  of  his  destiny  fur- 
nished him  the  opportunity  by  forcing  him  into  a  prob- 
lem apparently  entirely  different,  the  study  of  beers. 


PASTEUR 
(From  a  steel  engraving  by  Manesse,  Minerva,  Vol.  Ill,  1894.) 


SIXTH  PART 
Studies  on  Beer 

I 
STUDIES  ON  BREWING 

These  studies  were  begun  in  1871,  in  my  laboratory 
in  the  Faculty  of  Sciences  of  Clermont-Ferrand,  and  in 
the  chemical  laboratory  of  the  School  of  Medicine  of  the 
same  town.  They  were  undertaken  without  any  definite 
aim,  simply  to  occupy  the  enforced  leisure  which  the 
Commune  and  the  Siege  of  Paris  gave  to  Pasteur.  He 
had  at  once  set  himself  to  work  to  contribute  his  knowl- 
edge which  was  already  great,  as  his  share  in  the  rehabili- 
tation of  his  humiliated  country.  He  already  dreamed 
of  a  Pasteur  Institute  where  he  would  be  surrounded 
by  all  of  his  assistants  and  where  he  would  lead  them 
on  to  new  victories.  "I  have  a  head  full  of  the  most 
beautiful  projects  for  work,"  he  wrote  me  March  29, 
1871.  "The  war  has  forced  my  brain  to  He  fallow. 
I  am  ready  for  new  productions.  Alas!  Perhaps 
I  am  laboring  under  an  illusion.  In  any  case  I  shall 
make  the  attempt.  Oh!  why  am  I  not  rich!  A 
millionaire!  I  would  say  to  you,  to  Raulin,  to  Gernez, 
to  Van  Tieghem,  etc.  Come  !  We  will  transform  the  world 
by  our  discoveries  !  How  fortunate  you  are  to  be  young 
and  to  have  good  health!  O,  that  I  could  begin  a  new 
life  of  study  and  work!  Poor  France,  dear  land  of  our 
fathers!  Why  can  I  not  help  to  lift  you  up  once  more 
from  your  disasters?" 

While  waiting  to  engage  in  the  great  schemes,  the 

187 


188  pasteur:  the  history  of  a  mind 

thought  of  which  already  haunted  him,  he  allowed  him- 
self to  be  seduced  by  the  idea  of  studying  the  manufac- 
ture of  beer.  Was  it  not  possible  to  make  it  in  France 
as  well  as  in  Germany,  and  to  free  us  through  science 
from  paying  tribute  to  the  breweries  across  the  Rhine? 
Such  was  the  ambition  that  took  possession  of  him  little 
by  little  as  he  penetrated  more  and  more  into  this  dim- 
cult  subject.  To-day  we  may  say  that  this  ambition 
has  been  realized  as  much  by  the  efforts  of  Pasteur  as 
by  the  intelligent  activity  displayed  by  the  French 
brewers.  At  the  present  time,  the  best  French  beers 
are  equal  to  the  best  German  or  Austrian  beers,  and  for 
this  progress  the  French  brewers,  in  the  Congress  of 
1889,  gave  the  honor  and  credit  to  the  labors  and  to  the 
book  of  Pasteur  on  beer. 

This  book  is  not  an  ordinary  book,  not  a  kind  of 
theoretical  treatise  on  brewing.  It  reflects  so  clearly 
the  varied  preoccupations  of  Pasteur  at  this  stage  of  his 
existence,  that  I  am  obliged  to  draw  attention  to  its 
somewhat  eccentric  composition.  Of  brewing  there  is 
very  little  said.  The  first  chapter  shows  that  the  dis- 
eases of  beer  are  always  due  to  the  development  of 
microscopic  organisms  foreign  to  a  good  fermentation, 
not  at  this  time  a  new  idea.  The  last  chapter  gives  the 
means  of  making  pure  and  unalterable  beers.  And  it 
seems,  in  reality,  that  this  is  sufficient,  and  that  one 
might  be  content  with  saying  to  the  brewers:  This  is 
why  your  beers  are  bad,  and  here  is  the  means  of  making 
good  ones! 

It  was,  in  fact,  in  these  relatively  simple  terms  that 
Pasteur  stated  the  problem  in  the  beginning.  But  he 
was  not  slow  to  see  that  the  question  was  much  more 
complicated.  An  egg  of  a  silkworm  developed  accord- 
ing to  a  scientific  formula  is  surely  a  good  egg.  A  beer 
protected  from  pathogenic  ferments  during  its  manufac- 


STUDIES   ON  BREWING  189 

ture  is  not  necessarily  a  good  beer.  Questions  of  taste 
enter  into  the  judgment  of  beer,  that  is  to  say,  the  least 
scientific  thing  in  the  world,  the  most  variable,  and  the 
most  difficult  to  grasp.  This  complex  taste,  to  which 
each  brewery  accustoms  its  patrons,  depends  at  the 
same  time  on  the  original  material  used,  on  the  yeast, 
on  the  water  employed  in  the  brewing,  and,  in  a  much 
greater  measure  than  one  would  believe,  on  all  the  varied 
processes  of  the  manufacture.  So  that  the  problem 
was  not  that  of  making  a  good  beer,  but  of  making 
many  good  beers,  differing  each  from  the  other,  and  re- 
producing for  each  brewery  the  type  to  which  its  patrons 
had  become  accustomed 

Now,  for  this  work  of  adaptation  and  detail  Pasteur 
lacked  a  very  necessary  qualification.  He  did  not  like 
beer,  and  although,  as  the  result  of  exercise  and  volition, 
he  finally  succeeded  in  developing  a  taste  for  it  and  a 
sufficiently  trained  palate,  he  remained  insensible  to 
differences  which  the  brewers  extolled,  and  which  he 
was  sometimes  stupefied  to  see  exquisitely  appreciated 
also  by  his  friend,  Bertin,  who  was  his  neighbor  in  the 
Normal  School,  and  who  was  frequently  invited  to  the 
laboratory  for  the  tasting  séances.  At  the  joyous 
railleries  with  which  his  friend  sometimes  plied  him, 
Pasteur  was  disconcerted,  knowing  that  they  were  carry- 
ing him  into  regions  which  he  did  not  desire  to  enter, 
and  he  might  have  renounced  immediately  this  labor  of 
Sisyphus,  if  he  had  not  had  the  imprudence  to  solicit 
the  pecuniary  aid  of  a  brewing  school  which  was  very 
large  and  generous,  but  with  which  he  had  contracted 
the  moral  obligation  of  succeeding  in  his  enterprise. 

It  is  not  simply  a  bad  play  on  words  to  say  that  he 
has  never  become  master  of  his  subject,  because  he  has 
never  been  possessed  by  it.  There  was  no  longer  that 
profound  absorption  in  his  work  so  evident  in  his  study 


190  pasteur:  the  history  of  a  mind 

on  crystals,  on  spontaneous  generation,  and  on  silk- 
worms. At  every  instant  his  thoughts  and  his  actions 
got  away  from  him  without  his  being  conscious  of  it, 
attracted  by  some  question  which  seemed  to  him  more 
important  than  the  influence  of  the  degree  of  aeration 
of  the  must  on  the  quality  of  the  beer,  and  it  is  this 
which  we  see  in  his  book,  where  he  attacks  and  solves  a 
multitude  of  questions  which  have  only  a  remote  con- 
nection with  the  brewery.  The  studies  on  the  trans- 
formation of  species,  one  into  another,  on  the  first  origin 
of  the  yeasts  of  the  vintage,  on  the  general  theory  of 
alcoholic  fermentation,  fill  three-fourths  of  the  book. 
His  obviously  desultory  style  renders  its  analysis  difficult. 
We  shall  consider  it,  en  bloc,  only  as  a  document  which 
is  of  great  value  for  the  history  of  the  scientific  man  who 
composed  it. 

There  is  another  way  of  tracing  the  preoccupations 
of  Pasteur  at  this  time;  that  is  to  examine  the  Comptes 
rendus  de  V Académie  des  Sciences.  The  Academy  served 
him  both  as  a  tribune  from  which  to  reply  to  his  oppo- 
nents without,  and  as  a  field  of  combat  for  the  discus- 
sions, sometimes  picturesque,  into  which  he  entered  with 
some  of  his  confrères.  All  this  part  of  his  life  forms  an 
animated  picture.  Let  us  endeavor  to  trace  the  prin- 
cipal facts  without  following  strictly  the  chronological 
order. 

II 

TRANSFORMATION  OF  ONE  SPECIES  INTO 
ANOTHER 

There  is  in  the  beginning  one  part  with  which  we  are 
already  familiar,  through  having  encountered  it  in  its 
proper  place.  That  is  the  whole  discussion  with  Bastian 
on  spontaneous  generations,  and  with  Liebig  on  the  rôle 


TRANSFOEMATION  OF  ONE  SPECIES  INTO  ANOTHER      191 

of  ferments  in  fermentation.  We  have  seen  that  Pasteur 
had  come  to  know  that  the  air  was  not  that  receptacle 
for  germs,  that  redoubtable  enemy  which  he  had  hitherto 
supposed  it  to  be,  and  had  convinced  himself  that, 
provided  the  liquids  were  well  sterilized  in  the  auto- 
clave and  the  flasks  in  an  oven,  it  was  possible  to  work 
with  some  security  in  contact  with  air,  and  not  have  to 
fear  too  much  the  entrance  of  germs  from  this  source. 
All  our  present  technique  has  come  from  these  ideas. 
Personally  Pasteur  was  indifferent  to  perfection  of 
technique;  the  complexity  of  his  apparatuses  was  of 
little  importance  to  him.  He  only  required  that  they 
should  be  reliable,  and  answer  the  questions  he  asked 
without  ambiguity.  But  accuracy  and  facility  or 
rapidity  of  question  and  answer  may  go  hand  in  hand. 
This  is  the  rôle  of  a  good  technique.  That  which  has 
come  out  of  the  laboratory  of  Pasteur  was  the  offspring  of 
the  ideas  and  discoveries  of  the  master;  but  it  is  only  just 
to  say  that  it  was  created  by  the  three  collaborators 
whom  Pasteur  had  the  good  fortune  to  encounter  at 
this  time — Joubert,  Chamberland  and  Roux. 

Pasteur  needed  another  thing  for  approach  to  the 
domain  of  pathology,  which  every  circumstance  invited 
him  to  enter.  He  saw  the  germ  theory  inspire  the  works 
of  Davaine  on  the  anthrax  bacteridium,  the  startling 
experiment  of  M.  Chauveau  on  castration  by  sub- 
cutaneous torsion  (bistournage) ,  Alphonse  Guérin's  new 
method  of  dressing  wounds,  the  researches  of  M.  Guyon 
on  antiseptic  washings  of  the  bladder  and  of  the  urethra. 
He  had  applauded  in  1871  Dr.  Déclat's  successful 
experiments  in  the  antiseptic  dressing  of  wounds;  he 
did  not  yet  know  the  work  of  Lister  in  antiseptic  surgery, 
which  has  opened  a  new  era,  but  he  was  not  slow  in 
finding  it  out  and  admiring  it.  But  in  order  to  approach 
the  promised  land  of  which  he  dreamed,  and  especially 


192  pasteur:  the  history  of  a  mind 

to  do  so  with  security,  he  had  need  of  an  equipment 
of  facts  and  ideas  which  he  did  not  yet  possess,  and  which 
his  opponents  forced  him  to  acquire. 

The  most  remarkable  example  I  can  cite  in  support  of 
what  I  wish  to  say  comes  from  the  discussion  with 
Trécul,  who,  renewing  an  opinion  introduced  into  science 
by  Turpin  and  later  supported  by  Bail,  Berkeley, 
Hoffmann,  Hallier,  admitted  the  transformation  of 
microscopic  species,  one  into  another.  This  was  denying 
the  specificity  of  the  germ  established  by  the  first 
labors  of  Pasteur  on  fermentations,  and  Pasteur  had 
combatted  this  opinion,  beginning  in  1861  in  the  Bulletin 
de  la  Société  philomathique.  To  comprehend  what 
obscurities  this  theory  would  have  introduced  into 
microbian  pathology,  it  is  sufficient  to  recall  that  a 
denial  of  the  specificity  of  the  germ  would  have  contro- 
verted the  present  day  belief  in  the  specificity  of  disease. 
It  was,  therefore,  important  that  it  should  be  rooted  out 
of  all  minds. 

Unquestionably,  it  was  not  the  demonstrations  of 
Bail,  of  Hoffmann,  or  even  those  of  Trécul  which  could 
give  credit  to  this  theory.  All  these  eminent  botanists 
were  poor  experimenters,  going  out  to  meet  sources  of 
error,  not  to  bar  the  way,  so  to  speak,  but  to  open  it  up  to 
them.  But  favoring  this  idea  of  the  mutability  of 
species  was  the  doctrine  of  spontaneous  generation, 
which  found  in  this  mutability  one  of  its  arguments. 
There  were  the  new  ideas  introduced  by  Darwin  and  the 
school  of  evolutionists.  Finally,  and  this  was  more 
grave,  Pasteur  himself,  the  greatest  authorized  exponent 
of  the  opposite  school,  or  rather  of  the  experimental 
method,  rejected,  in  the  name  of  experimentation, 
the  transformation  of  yeast  into  Pénicillium  glaucum, 
but  accepted  that  of  the  Mycoderma  vini,  or  flowers  of 
wine,  into  an  alcoholic  ferment  under  certain  conditions. 


TRANSFORMATION  OF  ONE  SPECIES  INTO  ANOTHER      193 

On  sweetened  wine  or  must  of  beer,  exposed  in  a 
shallow  porcelain  basin,  he  sowed  some  mycoderma  which 
formed  a  pellicle  on  the  surface.  He  then  submerged 
this  pellicle,  thoroughly  shaking  the  liquid  in  order  to 
dislocate  and  moisten  all  parts  of  it.  Then  he  introduced 
the  whole  into  a  flask  which  he  filled  completely  full  and 
which  he  closed  with  a  stopper  to  which  was  attached  a 
tube,  the  opposite  end  of  which  opened  under  water 
so  as  to  allow  no  contact  of  air  with  the  liquid.  In  this 
closed  flask  he  saw  a  true  fermentation  take  place,  which 
he  attributed  to  the  transformation  of  the  mycoderma 
cells  into  yeast. 

At  Clermont,  where  Pasteur  did  me  the  honor  of 
working  in  my  laboratory,  we  repeated  this  experiment 
several  times,  and  as  I  was  naturally  more  intransigent 
than  he,  being  his  pupil,  I  refused  to  yield  to  this  proof, 
and  I  objected  to  the  possible  presence  of  globules 
of  yeast  derived  from  the  air,  from  the  water,  or  from 
the  flasks  before  or  after  the  filling,  in  spite  of  the  pre- 
cautions taken  to  avoid  it.  Pasteur  resisted  because, 
in  his  mind,  this  fact  was  related  to  other  ideas  which 
we  shall  encounter  soon,  and  which  are  relative  to  the 
general  theory  of  fermentation.  The  experiment,  further- 
more, sometimes  succeeded  with  a  clearness  which  made 
it  convincing  and  closed  my  mouth.  In  short,  Pasteur 
had  reported  his  conviction  in  Paris,  and  it  reappears 
several  times  in  his  Notes  of  1872  and  1873  before  the 
Academy  of  Sciences. 

If  I  recall  this  fact,  it  is  because  Pasteur  loved  to  cite 
it  himself  as  an  example  of  the  ease  with  which  the 
least  preconceived  idea  leads  even  the  most  alert  observer 
into  error.  Thus  it  is  that  he  has  taken  pains  to  re- 
count how  he  discovered  his  self-deception.  It  is  in- 
teresting to  see  his  mind  at  work  in  one  of  the  thousand 
details  of  his  scientific  fife. 

13 


194  pasteur:  the  history  of  a  mind 

"In  the  experiments  conducted  as  I  have  just  de- 
scribed, the  yeast  which  comes  into  existence,  and  which 
very  promptly  causes  an  active  alcoholic  fermentation, 
is"  introduced  originally  by  the  atmospheric  air,  which 
allows  the  germs  to  fall  either  upon  the  mycoderma 
pellicle  or  the  objects  which  are  used  during  the  succes- 
sion of  manipulations.  Two  circumstances  of  these 
experiments  gave  me  warning  of  the  existence  of  this 
cause  of  error.  It  sometimes  happened  that  I  found 
among  the  cells  of  the  mycoderma  in  the  bottom  of 
the  flasks  where  I  had  submerged  the  flowers  of  wine, 
some  large  spherical  cells  of  Mucor  mucedo  or  racemosus, 
yeastlike  cells  with  which  we  shall  soon  become  familiar 
in  studying  this  curious  mold.  Since  there  is  present 
Mucor  mucedo  or  racemosus,  although  I  had  sown  only 
Mycoderma  vini,  it  must  be,  I  said  to  myself,  that  one 
or  several  spores  of  this  Mucor  have  been  introduced 
by  the  ambient  air.  Now,  if  the  air  brings  the  spores 
of  Mucor  into  my  operations,  why  would  it  not  bring  the 
cells  of  yeast,  especially  in  my  laboratory?  Further- 
more, it  happened  that  in  a  number  of  the  experiments 
which  I  repeated  many  times,  under  the  pressure  of  my 
doubts,  and  in  which  I  did  not  grow  weary  of  searching 
for  this  desirable  transformation  which  accorded  so  well 
with  the  physiological  theory  of  fermentation  to  which 
I  had  been  led,  some  had  a  negative  result,  that  is  to  say 
the  transformation  of  the  mycoderma  into  yeast  did 
not  occur,  although  the  conditions  were  as  similar  as 
one  could  wish  to  those  of  the  experiments  in  which  I 
saw  it  take  place.  Why,  thought  I,  this  inactivity 
in  the  cells  of  the  mycoderma?  Even  in  the  most 
favorable  cases  of  the  supposed  transformation  it  hap- 
pened without  doubt  that  a  multitude  of  cells  of  Myco- 
derma vini  did  not  become  yeast  cells,  but  how  admit 
that   among  the  billions  of  submerged   cells  all  were 


TRANSFORMATION  OF  ONE  SPECIES  INTO  ANOTHER       195 

unfitted  for  transformation,  if  this  transformation  were 
really  possible? 

"It  was,  then,  to  avoid  this  embarrassment,  that  I 
resolved  to  modify  entirely  the  conditions  of  the  ex- 
periment, and  to  apply  to  the  research  which  I  had  in 
view  a  culture  method  which  would  suppress  completely, 


Fio.  14.— Flask  used   by  Pasteur  in  his  study  of  the  transformation    of 

species. 

or  at  least  very  nearly,  the  sole  cause  of  error  which  I 
had  encountered,  that  is  the  possible  falling  of  germs  or 
of  yeast  cells  from  the  air  during  the  manipulation."1 

To  carry  out  this  idea,  Pasteur  added  to  the  flask 
with  the  curved  neck  which  he  had  used  in  his  studies  on 
spontaneous  generations,  a  second  tubulure   (Fig.   14) 

1  Études  sur  la  bière,  p.  118. 


196 


pasteur:  the  history  of  a  mind 


permitting  the  inoculation  of  the  liquid  by  removing 
the  glass  stopper  which  closed  the  rubber  tube  attached 
to  the  straight  tubulure.  In  this  flask  the  culture  is  in 
contact  with  air.  When  there  is  need  of  provoking  a 
fermentation  in  the  absence  of  air,  the  straight  tubulure 
is  connected  by  means  of  its  rubber  tube  with  a  matrass 
sufficiently  smaU  for  the  liquid  to  fill  it  completely. 
In  order  to  make  with  this  apparatus  a  study  of  the 
transformation   of   the    mycoderma   into   yeast,   it   is 


Fig.  15. — Apparatus  used  by  Pasteur  in  his  study  of  alcoholic  and  other 

fermentations. 


sufficient  to  sow  with  the  flowers  of  wine  an  alcoholic 
liquid,  or  a  sugar  solution  placed  in  D,  and  to  pour  it 
immediately,  when  the  pellicle  has  formed,  into  the 
matrass  BC,  where  it  finds  the  conditions  of  great  depth 
and  of  small  free  surface  existing  in  the  flask  of  the  first 
experiment  (Fig.  15).  The  details  of  the  manipulation 
necessary  to  realize  this  transfer  in  the  absence  of  all 
exterior  germs  are  of  little  moment.  The  apparatus  is, 
furthermore,  complicated  and  has  been  advantageously 
replaced    since.     It    suffices,    however,    to    attain   the 


TRANSFORMATION  OF  ONE  SPECIES  INTO  ANOTHER     197 

desired  end,  which  is  the  comparative  study  of  the  same 
mycoderma  on  the  surface  and  in  the  depths. 

"Never  again,"  continues  Pasteur,  "did  I  see  the 
yeast  or  an  active  alcoholic  fermentation,  following  the 
submersion  of  the  flowers,  either  in  the  flasks  or  in  the 
matrasses  connected  with  these  flasks.  .  .  .  At  a  time 
when  ideas  on  the  transformation  of  species  are  so 
easily  adopted,  perhaps  because  they  dispense  with 
rigorous  experimentation,  it  is  not  without  interest  to 
consider  that  in  the  course  of  my  researches  on  the  culture 
of  microscopic  plants  in  the  pure  state,  I  have  once  had 
occasion  to  believe  in  the  transformation  of  one  organism 
into  another,  in  the  transformation  of  the  Mycoderma  vini 
or  cerevisiœ  into  yeast,  and  that,  this  time,  I  was  in 
error.  I  did  not  know  how  to  avoid  the  cause  of  error 
which  my  justified  confidence  in  the  germ  theory 
had  led  me  to  discover  so  often  in  the  observations  of 
others." 

The  same  flask  with  two  tubulures  served  Pasteur  to 
show  that  the  alcoholic  yeast  is  not  transformed  into  a 
lactic  ferment,  as  J.  Duval  said,  nor  into  Pénicillium  or 
Aspergillus,  as  Hoffmann  maintained;  that  this  yeast, 
itself,  did  not  come  from  the  transformation  of  the 
spores  of  Pénicillium,  as  Trécul  said;  nor  furthermore 
did  the  Mycoderma  aceti  yield  the  bacteria  which 
Béchamp  believed  he  saw  derived  from  it.  In  short, 
the  idea  of  species  was  saved  for  the  time  being  from  the 
attack  which  was  directed  against  it,  and  it  has  not 
been  contested  seriously  since  that  time,  at  least  on  this 
ground. 


198  pasteur:  the  history  of  a  mind 

III 
ANAEROBIC  LIFE  OF  AEROBIC  SPECIES 

In  exchange,  Pasteur  had  the  sorrow  of  seeing  ruined 
one  of  the  arguments  most  favorable  to  his  physiological 
theory  of  fermentation.  But  he  ought  not  to  have  been 
slow  to  congratulate  himself  upon  this  slight  check, 
because  behind  the  fallen  argument  there  arose  another 
still  more  convincing,  which  the  first  had  masked.  It 
sufficed  him,  in  order  to  find  it,  to  repeat  with  Mucor 
mucedo  the  preceding  experiments. 

Bail  had  announced  in  1857  that  this  mucor  which 
lives  the  life  of  an  aerobic  plant,  when  in  contact  with 
air,  can,  when  submerged  in  the  absence  of  air,  produce 
a  very  active  alcoholic  fermentation. 

There  are  fouud  then  in  the  liquid,  instead  of  more  or 
less  septate  mycelial  filaments  which  serve  to  some 
extent  as  roots  for  this  plant,  chains  of  round  or  oblong 
cells,  which  Bail  had  taken  for  the  cells  of  yeast  of  beer. 
Repeating  these  experiments  under  the  pure-culture 
conditions  which  we  have  described,  Pasteur  determined 
that  these  affirmations  were  exactly  true.  Submerged 
and  in  the  absence  of  air,  the  mycelium  of  the  fungus 
becomes  very  much  septate,  being  transformed  into  a 
chain  of  cells;  simultaneously  bubbles  of  carbonic  acid 
are  given  off,  and  alcohol  is  present  in  the  liquid.  What 
is  the  explanation  of  this?  Is  this  mucor  then  an  ex- 
ception? Can  it  undergo  transformation  into  yeast? 
This  was  the  opinion  of  Bail;  but  we  shall  soon  see 
how  much  was  gained  by  going  below  the  surface  of 
this  question.  From  this  apparently  insignificant  fact, 
Pasteur  has  evolved  a  whole  theory  of  fermentation. 

In  order  to  place  these  phenomena  in  their  proper 
light  we  shall  suppose  that  Pasteur  treated  them  as 


PASTEUR 
(From  a  common  photo.) 


ANAEROBIC    LIFE    OF   AEROBIC    SPECIES  199 

was  his  ordinary  custom,  that  is,  that  immediately 
following  their  discovery,  he  combined  them  in  a  syn- 
thetic experiment.  If  he  had  wished  to  pursue  that 
course  in  this  case,  the  following  undoubtedly  would 
have  been  his  method  of  procedure. 

Into  a  series  of  flasks  with  two  tubulures  like  those 
we  have  just  described,  each  one-third  filled  with  steril- 
ized must  of  beer,  he  would  have  introduced,  by  remov- 
ing for  an  instant  the  glass  stopper  closing  the  rubber 
tube,  a  small  platinum  wire  which  had  been  flamed  and 
passed  over  a  spore-bearing  culture  of  the  mucor.  He 
would  then  have  flamed  the  stopper  and  replaced  it. 

Let  us  take  for  example  the  three  Mucedinese  studied 
by  Pasteur,  Pénicillium  glaucum,  Aspergillus  niger, 
and  the  Mucor  mucedo.  That  makes  three  flasks.  At 
the  end  of  24  or  48  hours,  the  spores  introduced  by  the 
platinum  wire  will  have  produced  a  branching  mycelium, 
which  if  well  aerated  produces  aerial  branches  sur- 
mounted by  tufts  of  young  spores;  but  at  the  bottom 
of  these  flasks,  which  communicate  with  the  exterior 
only  by  means  of  a  long  capillary  neck,  our  mycelia 
have  only  an  insufficient  quantity  of  air  and  they 
fruit  little  or  not  at  all,  but  nevertheless  in  time  they 
oxidize  completely  the  sugar  on  which  they  live. 

Before  the  sugar  has  disappeared  let  us  connect  as 
before  the  straight  tubulures  of  each  of  the  flasks  with 
a  smaller  matrass  which  the  liquid  will  fill  up  to  the 
neck,  and  let  us  pour  the  liquid  into  it.  In  its  new 
receptacle,  this  must  of  beer  will  be  less  exposed  to  air 
than  before.  We  might  even  say  that  it  has  no  air  at 
all  at  its  disposal,  for  the  mycelium  has  caused  all  that 
which  was  in  the  solution  to  disappear,  and  has  replaced 
it  by  the  carbonic  acid  which,  being  given  off  from  the 
surface  of  the  latter,  prevents  the  arrival  of  new  oxygen. 
Under  these  conditions,  we  find  that  the  mycelium  of 


200  pasteur:  the  history  of  a  mind 

Pénicillium  rapidly  suspends  its  action  and  becomes  inert  ; 
the  mycelium  of  Aspergillus  continues  a  little  longer  to 
consume  the  sugar,  but  its  growth  is  also  soon  arrested. 
Only  the  mycelium  of  Mucor  endures  for  several  hours 
this  deprivation  of  air.  It  becomes  foamy  as  the  result 
of  an  ebullition,  abundant  at  first  then  more  slow,  of 
bubbles  of  carbonic  acid  ;  and  we  find  in  the  liquid  very 
perceptible  quantities  of  alcohol.  In  short,  to  the  com- 
plete combustion  which  the  mucor  gives  in  contact  with 


Fig.  16. — Yeast-like  forms  assumed  by  Mucor  mucedo  in  the  absence 

of  air. 

air,  there  succeeds,  without  transition  and  without  ap- 
parent difficulty,  at  least  in  the  beginning,  a  partial 
combustion  in  the  form  of  an  alcoholic  fermentation. 
Singularly,  the  mycelium  of  the  plant  becomes  modi- 
fied under  these  new  conditions  of  existence;  that  of  the 
Pénicillium  remains  almost  as  it  was;  that  of  the  Asper- 
gillus segments  and  in  place  of  the  branching  filaments 
has  chains  of  cells.  It  is  in  the  mycelium  of  the  Mucor 
that  the  changes  are  the  most  marked.  As  long  as  the 
fungus  is  living  as  a  mold  in  free  contact  with  air,  its 


ANAEROBIC   LIFE   OF   AEROBIC    SPECIES  201 

mycelial  filaments  are  slender,  branching,  and  inter- 
twined, but  when  it  becomes  a  ferment  as  the  result  of 
an  insufficient  supply  of  air,  the  hyphse  segment,  sepa- 
rate, enlarge,  and  finally  are  transformed  into  chains 
of  large,  round,  or  slightly  oval  cells  (Fig.  16)  which, 
in  reality,  resemble  large  cells  of  yeast.  Bail  had  be- 
lieved in  their  transformation,  but  Pasteur  shows  that 
when  these  supposed  yeasts  are  introduced  into  aerated 
must  of  beer  they  do  not  produce  alcoholic  fermenta- 
tion: they  reproduce  the  Mucor.  There  has  not,  there- 
fore, been  any  transformation  of  species;  there  has 
been  only  an  adaptation  to  a  new  life,  with  a  change  of 
form  corresponding  to  change  of  functions. 

When  he  had  reached  this  point,  Pasteur  might  recall 
that  there  are  analogous  changes  in  the  mycoderma  of 
wine  when  submerged  in  a  sugar  solution.  The  cell 
becomes  more  turgescent,  its  protoplasm  less  granular 
(Fig.  13).  The  mueor  and  the  mycoderma,  so  different 
in  form,  resemble  each  other,  therefore,  in  their  nature. 
In  the  case  of  both,  and  of  a  certain  number  of  other 
lower  species,  the  fermenting  property,  that  is  to  say 
the  ability  to  break  up  sugar  into  alcohol  and  carbonic 
acid,  appears  to  us,  therefore,  not  as  a  specific  property 
but  as  a  transitory  faculty  related  to  the  conditions  of 
existence,  and  we  may  briefly  sum  up  the  foregoing  by 
saying  that  fermentation  is  life  without  air. 
W  When  Pasteur  gave  utterance  to  these  facts  before 
the  Academy  of  Sciences,  he  was  not  understood  at 
first,  and  his  opponents  shouted  cries  of  victory.  This 
modification  of  form  accompanying  a  modification 
of  properties  was  transformation,  as  much  as  that  of 
Hoffmann,  or  Turpin,  or  that  of  Darwin.  No,  Pasteur 
unceasingly  repeated,  it  is  not  a  question  of  a  trans- 
formation of  species  but  of  a  general  physiological  law 
which  is  applicable  alike  to  all  living  species  and  respects 


202  pasteur:  the  history  of  a  mind 

their  individuality.  It  is  a  question  of  a  functional 
elasticity  of  the  cell,  permitting  it  to  adapt  itself  without 
changing  its  nature,  to  be  and  to  become  according  to 
varied  conditions  of  existence.  We  see  to  what  heights 
he  had  raised  the  debate:  by  changing  the  mode  of 
interpretation  of  facts  already  known,  he  caused  them  to 
give  birth  to  a  new  theory. 


IV 

AEROBIC  LIFE  OF  ANAEROBIC  SPECIES 

The  preceding  facts  had  in  reality  a  bold  counter- 
part. We  have  just  seen  that  some  species,  aerobic 
under  ordinary  conditions,  can  lead  an  anaerobic  life 
for  a  greater  or  less  length  of  time.  In  like  manner 
we  ought  to  be  able  to  acclimate  a  species  which  is 
ordinarily  anaerobic  to  an  aerobic  life. 

Such  is  the  yeast  of  beer.  Let  us  try  first  to  ascertain 
just  how  far  it  can  go  in  its  anaerobic  life  by  sowing  it 
in  a  nutrient  solution  which  we  have  completely  de- 
prived of  oxygen,  it  matters  not  how.  In  this  dis- 
aërated  medium  the  yeast  lives,  but  feebly;  its  develop- 
ment is  slow,  and  the  fermentation  takes  a  long  time. 
But  it  comes  to  an  end,  and  if,  when  it  has  terminated, 
we  investigate  the  relation  between  the  weight  of  the 
sugar  transformed  and  the  weight  of  yeast  present  we 
find  a  very  high  figure,  of  150  to  200.  If,  for  example, 
we  work  with  100  grams  of  sugar,  we  shall  see  that  from 
5  to  7  decigrams  of  yeast  have  been  sufficient  to  trans- 
form it  into  alcohol  and  carbonic  acid. 

Let  us  now  give  to  the  yeast  a  little  more  air.  Let  us 
sow  it  in  a  fermentable  aerated  liquid,  contained  in  a 
flask  which  we  shall  not  fill  completely,  so  that  the  yeast 


AEROBIC    LIFE    OF   ANAEROBIC   SPECIES  203 

has  at  its  disposal  for  its  needs  the  oxygen  dissolved 
in  the  liquid,  and  a  little  free  oxygen  in  the  air  of  the 
flask.  This  time  life  is  more  active,  fermentation 
more  rapid,  reproduction  of  the  yeast  more  abundant,  and 
for  100  grams  of  sugar  transformed  we  have  about 
1.5  grams  of  yeast  produced. 


Fig.  17. — Left  side:  disjointed   cells  ol   old  yeast.     Right    side:  Their  re- 
juvenation in  a  sugared  must. 

Let  us  go  a  step  further  in  the  process  of  aeration. 
Let  us  spread  out  our  sugar  solution  over  a  broad 
surface  or  shake  it  in  contact  with  air,  so  that  each 
yeast  cell  finds  itself  constantly  in  contact  with  the 
free  oxygen  of  which  it  has  need.  This  time,  the  sugar 
disappears  [rapidly;  it  no  longer  gives  alcohol,   or  at 


204  pasteur:  the  history  op  a  mind 

least  gives  very  little;  it  is  a  complete  combustion  which 
has  followed  the  incomplete  combustion  of  the  preced- 
ing experiment  in  the  same  way  as  an  incomplete  com- 
bustion followed  a  complete  one  in  the  case  of  the 
mucor  when  deprived  of  air.  Finally,  a  last  analogy: 
the  yeast,  like  the  mucor,  multiplies  and  increases  mark- 
edly in  weight  in  contact  with  air,  so  that,  this  time, 
for  100  grams  of  sugar  used,  we  find  20  to  25  grams  of 
yeast  produced. 

Some  modifications  of  form  accompany  here  al  o  these 
changes  of  function.  The  yeast  in  contact  with  air  is 
less  full  of  cavities,  has  a  much  finer  content,  and  is 
younger  in  aspect,  as  the  comparison  of  the  two  halves 
of  Fig.  17  shows. 

In  this  very  aerobic  existence,  the  yeast,  therefore, 
approaches  the  Mucedinese.  It  differs  from  them 
in  that  it  can  lead  the -anaerobic  life,  to  which  it  is  adapted 
for  a  very  much  longer  time,  than  even  the  Mucor. 
But  here  also,  the  appearance  of  the  ferment-character 
accompanies  life  without  air. 

So  that  in  the  presence  of  the  general  character  of 
these  facts,  Pasteur  had  been  led  to  ask  himself  the 
following  question  :  Can  we  admit  that  the  yeast  and  the 
other  plants  capable  of  becoming  alcoholic  ferments 
which  absorb  and  consume  oxygen  so  actively  when 
they  have  it  at  their  disposal,  cease  to  have  need  of  it 
when  it  is  refused  them,  and  in  this  case  change  com- 
pletely their  mode  of  existence?  If  we  reply,  "Yes," 
to  this  question,  then  there  is  no  relation  between 
aerobic  and  anaerobic  life.  These  are  two  different 
living  organisms  which  succeed  each  other  in  the  same 
protoplasm  and  within  the  same  cell-wall.  If  we  admit, 
on  the  contrary,  as  it  is  evidently  more  natural  to  do, 
that  the  needs  of  the  cell  in  its  two  modes  of  existence 
remain  the  same,  and  that  only  the  means  of  satisfying 


AEROBIC   LIFE   OF   ANAEROBIC   SPECIES  205 

them  change,  then  the  appearance  of  the  ferment- 
character  is  connected  with  the  absence  of  oxygen,  and 
we  are  led  to  think  that  if  the  yeast  and  the  analogous 
plants  can  act  thus  on  sugar  during  their  anaerobic  life, 
it  is  because  they  have  the  ability  to  obtain  from  it  the 
oxygen  which  they  need,  the  oxygen  which  serves,  fur- 
thermore, for  their  respiration,  and  which  is  given  off 
at  once,  more  or  less  completely,  in  the  form  of  carbonic 
acid. 

According  to  this  conception,  every  living  cell  having 
need  of  oxygen,  if  deprived  of  this  gas  in  a  free  state,  and 
if  able  to  obtain  it  from  substances  which  contain  it  in 
a  combined  state,  would  be  a  ferment  for  these  substances. 
Here  is  a  theory  of  fermentation  very  directly  related  to 
the  facts,  as  we  have  come  to  see,  and,  furthermore,  very 
suggestive,  for,  if  it  notably  enlarges  the  field  of  cellular 
ferments,  it  at  the  same  time  restricts  the  field  of  fer- 
mentable substances  by  showing  that  only  those  sub- 
stances can  be  fermented  which  are  capable  of  furnishing 
to  their  ferment  the  oxygen  which  the  latter  uses  by 
burning  a  part  of  it.  Every  fermentable  substance  is 
capable,  consequently,  of  undergoing  an  internal  com- 
bustion, giving  off  heat  thereby,  for  since  there  is  a  life 
to  maintain,  it  is  necessary  that  there  be  somewhere  a 
source  of  energy.  The  living  organism  does  not  pro- 
duce it;  it  consumes  it  in  order  to  build  up  its  tissues, 
in  order  to  make  them  live.  So  that  a  fermentable 
substance,  before  producing  heat  by  undergoing  an 
internal  combustion,  becomes,  in  a  certain  measure, 
comparable  to  an  explosive  body,  gun-cotton  or  nitro- 
glycerin, which  burns  little  by  little  in  the  labora- 
tory of  the  yeast  cell.  Here  is  the  very  simple  con- 
ception which  Pasteur  called  the  physiological  theory  of 
fermentation. 

We  are  forced  to  believe  that  it  was  not  clear,  since, 


206  pasteur:  the  history  of  a  mind 

leaving  aside  the  DU  minores,  such  men  as  CI.  Bernard 
and  Berthelot  did  not  succeed  in  comprehending  it. 
It  is  true  that  only  with  difficulty  do  great  minds  under- 
stand one  another.  We  have  seen  Liebig  remain  deaf  to 
the  arguments  of  Pasteur  and  blind  to  his  demonstra- 
tions; we  are  going  to  see  the  same  struggle  in  the  dark 
follow  between  Bernard,  Berthelot  and  Pasteur. 


IDEAS  OF  CLAUDE  BERNARD  ON  FERMENTATION 

The  history  of  the  discussion  with  Bernard  is  curious 
in  that  Bernard  took  no  part  in  it,  and  that  Pasteur, 
was  obliged  to  debate  with  a  shade.  This  was  very 
painful  to  him.  Bernard  had  been  while  he  lived,  I  will 
not  say  a  confidant,  but  a  friend  with  whom  he  loved 
to  chat  during  the  séances  of  the  Academy  of  Sciences. 
These  séances  are  of  value  only  because  of  these  chats, 
and  it  would  be  beneficial  to  allow  them  to  go  on  freely 
in  the  salon,  while  the  Bureau  proceeded,  in  another 
part  of  the  building,  with  the  official  reception  of  notes 
and  memoirs.  We  may  well  believe  that  between  Bernard 
and  Pasteur,  who  occupied  neighboring  arm  chairs,  there 
was  no  question  of  religion,  politics  or  scandal.  They 
spoke  of  science  to  the  great  benefit  of  themselves  and 
of  others.  Theirs  were  two  powerful  minds,  concentrated 
in  their  work,  the  more  capable,  consequently,  of  a  mutual 
appreciation  and  understanding,  but  gaining  by  an 
exchange  of  blows  and  a  sharpening  of  wits  one  against 
the  other. 

Bernard,  toward  the  end  of  his  life,  had  been  led  to  a 
conception  of  the  phenomena  of  life  which  seemed  then 
and  still  seems  a  little  strange.     He  conceived  that  there 


IDEAS  OF  CLAUDE  BERNARD  ON  FERMENTATION   207 

were  in  the  living  organism  two  kinds  of  phenomena: 
the  phenomena  of  construction  or  synthesis,  which  alone 
he  considered  as  truly  vital,  and  the  phenomena  of  or- 
ganic destruction,  which  he  considered  to  be  of  a  physico- 
chemical  order.  In  a  word,  it  was  life  alone  which  was 
constructive,  leaving  to  the  forces  of  death  the  work  of 
destruction.  These  phenomena,  different  in  origin,  were, 
nevertheless,  not  separated  in  space  and  time.  Bernard 
admitted  that  there  were  phenomena  of  destruction  in 
the  living  cell,  and  that  whenever  a  muscle  contracts, 
a  gland  secretes  or  the  mind  works,  there  is  a  portion  of 
the  tissue,  muscular,  glandular  or  cerebral,  which  is 
destroyed.  But  although  simultaneous  and  correla- 
tive to  a  certain  degree,  these  phenomena  of  synthesis 
and  decomposition  were  none  the  less  of  different  essence, 
and  not  obedient  to  the  same  mechanism. 

Pasteur,  in  his  refutation  of  these  ideas,  does  not  seem 
to  me  to  have  perfectly  understood  them.  Bernard 
does  not  believe  at  all  as  Pasteur  thought,1  "in  a  forced 
opposition  between  the  phenomena  of  life  and  synthe- 
sis and  the  phenomena  of  death  and  destruction,  be- 
tween life,  properly  speaking,  and  fermentation."  At 
least  he  nowhere  says  so.  On  the  contrary  they  were, 
according  to  his  conception,  two  machines  which  con- 
curred in  the  same  work,  propelled  by  two  different 
motive  forces.  When  death  occurs  and  the  life-motor 
ceases  to  act,  the  second  motor  which  is  fed  by  com- 
bustions and  fermentations,  remains  in  action,  and  it  is 
that  which,  in  ways  purely  physical  or  chemical,  having 
no  longer  anything  vital,  presides  at  the  return  of  dead 
matter  to  the  ambient  nature. 

This  conception  did  not  contravene,  as  one  might 
believe  at  first,  the  demonstrations  of  Pasteur  on  the 

1  Examen  critique  d'un  écrit  posthume  de  M.  Bernard  sur  la  fermenta- 
tion, p.  47. 


208  pasteur:  the  history  of  a  mind 

subject  of  the  non-existence  of  spontaneous  genera- 
tions, and  on  the  subject  of  the  role  and  multiplica- 
tion of  the  ferment  in  fermentations.  Bernard  was  very 
respectful  when  face  to  face  with  facts,  but  when  he 
reflected  on  them  he  gave  himself,  as  he  had  every  right 
to  do,  a  great  liberty  of  interpretation.  Not  because 
one  salutes  another  is  he  obliged  to  think  well  of  him. 
Now,  on  reflection,  Bernard  came  to  approach,  little  by 
little,  the  stand  taken  by  Liebig,  and  asked  himself, 
for  it  was  still  only  the  period  of  hypotheses  and  of  brain- 
work  which  preceded  that  of  laboratory  work  in  his  case, 
asked  himself,  I  say,  whether,  perchance,  it  was  not 
in  virtue  of  the  second  mechanism  which  he  predicated, 
that  is  to  say  by  disassociation  and  destruction,  that  the 
microbes  caused  the  destruction  of  organic  matter. 

Unquestionably  a  mind  like  his  had  the  right  to  put 
these  questions  since  it  was  in  his  power  to  solve  them. 
If  he  could  show  that  the  best-known  phenomena  of 
organic  destruction,  the  transformation  of  sugar  into 
alcohol  and  carbonic  acid,  could  be  produced  entirely 
without  the  intervention  of  yeast  or  even  of  living  cells, 
by  the  natural  play  of  forces  exterior  to  the  cell,  and 
subject  only  to  the  laws  of  physics  and  chemistry,  what  a 
precious  confirmation  of  his  preconceived  ideas!  These 
physico-chemical  forces  could  not,  it  is  true,  be  common 
forces  taken  by  chance  from  the  ambient  nature.  Pas- 
teur had  shown  too  clearly,  apropos  of  spontaneous 
generations,  that,  reduced  to  these  forces  alone,  the  trans- 
formation of  dead  matter  was  a  very  slow  process.  But 
if  living  cells  are  needed  to  accelerate  this  transformation 
why  should  these  cells  not  act  by  manufacturing  and 
secreting,  on  the  vital  side  of  their  organization,  sub- 
stances capable  then  of  acting  outside  of  the  cell,  and  in 
a  physico-chemical  way?  The  yeast  secretes  a  diastase 
which,  outside  the  cell,  can  invert  cane-sugar.     Why 


IDEAS  OF  CLAUDE  BERNARD  ON  FERMENTATION   209 

should  it  not  secrete  another  diastase  capable  of  trans- 
forming sugar  into  alcohol  and  carbonic  acid?1 

Such  was,  at  least  as  far  as  we  can  see,  the  cycle  of 
ideas  which  Bernard  made  a  beginning  of  submitting 
to  experimental  verification  at  his  country  house  at 
Saint- Julien,  at  the  time  of  the  vintages  of  1877,  some 
months  before  his  death.  Without  saying  anything 
about  it  to  any  one,  he  had  written  down,  a  little  care- 
lessly, his  first  results  and  his  new  projects  for  experi- 
ments in  the  loose  leaves  of  a  manuscript  which  was 
found  after  his  death,  and  which  his  friends  believed 
worthy  of  publication.  It  is  always  necessary  to  dis- 
trust one's  friends,  especially  when  one  is  no  longer  there 
to  watch  them.  Posthumous  writings  have  never  aug- 
mented the  glory  of  any  one,  and  the  publication  of  these 
few  pages  of  notes,  which  Bernard  had  very  wisely  con- 
cealed at  the  bottom  of  a  drawer,  had  not,  in  my  opinion, 
any  pretext  or  excuse.  The  kind  of  general  ideas  in  the 
light  of  which  they  had  been  conceived  and  written  was 
sufficiently  well-known  by  the  recent  publication  of  the 
work  Sur  les  phénomènes  de  la  vie  communs  aux  animaux 
et  aux  végétaux,  the  proof  of  which  Bernard  had  carefully 
corrected  at  Saint- Julien  in  1877.  If  the  ideas  of  the 
master  had  undergone  a  little  change  since  then,  it  is 
not  to  be  observed  in  the  sybilline  phrases  of  the  manu- 
script. In  running  through  them  to-day,  it  seems  evi- 
dent that  Bernard  could  not  have  considered  his  work 
as  anything  more  than  a  blow  given  with  a  mattock 
in  order  to  test  the  soil  before  beginning  his  labors. 

1  We  now  know  that  it  does  do  this,  but  that  this  enzyme  (called  Zy- 
mase) can  be  obtained  for  study  only  by  crushing  the  yeast  under  high 
pressure.     Trs. 


210  pasteur:  the  history  of  a  mind 

VI 

DISCUSSION  OF  THE  IDEAS  OF  CLAUDE  BERNARD 

Assuredly,  in  the  presence  of  these  confused  experi- 
ments, published  without  the  consent  of  the  one  who 
made  them,  Pasteur  might  have  replied  only  with 
that  Olympian  silence  which  Bernard  would  certainly 
have  maintained  in  like  circumstances.  He  preferred 
ratherjto  do  what  he  had  always  done,  to  go  straight 
to  his  adversary  at  the  risk,  he  said,  of  encountering 
M.  Berthelot^behind  the  manuscript  of  Bernard.  To 
the  latter  he  replied  first:  "Your  diastase  which  makes 
alcohol?  Do  not  think  that  that  embarrasses  me.  I 
shall  be  happy  to  salute  it,  but  I  should  like  to  see  it  first. 
I  have  searched  for  it  and  never  found  it.  In  some 
recent  experiments  which  took  place  under  your  eyes, 
at  the  Academy,  and  which  met  with  your  approval, 
I  put  some  cells  of  the  grape,  taken  from  the  interior  of 
the  fruit,  into  a  sugar  solution  in  contact  with  pure  air 
and  I  have  found  neither  diastase  nor  alcohol  there. 
How  is  it  that  you,  to  whom  I  have  so  often  spoken  of  it, 
have  forgotten  or  been  unmindful  of  these  experiments? 

To  which  the  shade  of  Bernard  might  have  replied: 
"  Reassure  yourself,  my  friend,  I  am  not  unmindful  nor 
do  I  forget  anything!  But  because  you  have  not  seen 
a  thing,  does  not  prove  that  this  thing  is  impossible. 
In  order  to  demonstrate  the  existence  of  this  diastase 
I  make  other  conditions  than  yours.  I  take  grapes 
which  are  beginning  to  decay,  because  for  me  the  decay 
is  a  maturity,  not  advanced,  as  you  make  me  say  with- 
out, in  your  turn,  at  all  understanding  my  point  of  view, 
but  anticipatory,  that  is  to  say,  premature.  A  decayed 
grape  is  one  which  is  mature  before  the  others,  and  in 
which  are  beginning  the  phenomena  which  only  mani- 


DISCUSSION  OF  THE  IDEAS  OF  CLAUDE  BERNARD      211 

fest  themselves  later  in  its  sound  neighbors.  In  these 
decayed  grapes  I  find  alcohol.  I  find  it  also,  at  least 
so  I  believe,  in  the  dry  grapes,  and  I  see  there  no  cells  of 
yeast.  Thence,  the  idea  of  my  diastase.  It  may  very 
well  be  that  this  secretion  of  diastase  takes  place  only 
once,  and  that  I  came  at  a  fortunate  moment,  while 
you  were  too  early  or  too  late,  but  that  will  not  hinder 
us  from  remaining  good  friends. 

"Note  furthermore,"  Bernard  might  have  continued 
if  he  had  been  able  to  plead  his  own  cause,  or  if  he 
had  had  an  advocate,  "that  my  conception  is  in  accord 
with  some  of  the  experiments  which  you  cite  in  support 
of  yours.  MM.  Lechartier  and  Bellamy  before  you 
have  seen  fruits,  put  in  closed  flasks  in  the  presence  of 
air,  begin  by  absorbing  oxygen,  then  give  off  carbonic 
acid,  and,  furthermore,  produce  alcohol  by  an  interior 
fermentation  accomplished  without  the  aid  of  any  yeast 
cell.  It  is  one  of  the  experiments  which  you  cite  in 
support  of  your  ideas  of  life  without  air.  I  consider 
it  as  a  score  for  me,  and  I  say  that  the  results  of  MM. 
Lechartier  and  Bellamy  have  to  do  only  with  the  decay 
of  fruits  in  confined  atmospheres.  But  if  they  were 
rotted  in  contact  with  the  air  it  would  be  the  same,  as 
my  results  with  grapes  testify,  and  as,  I  hope,  the 
experiments  which  I  intend  to  make  on  apples  will 
also  testify." 

"But,"  responded  Pasteur,  "you  who  have  such  a 
good  memory  for  the  results  of  MM.  Lechartier  and 
Bellamy  who,  moreover,  are  in  accord  with  me,  how  is  it 
that  you  have  forgotten  my  experiments  in  which, 
instead  of  waiting  until  they  shall  have  consumed  the 
oxygen  of  the  air  with  which  they  are  in  contact,  I 
plunge  the  fruits  immediately  into  carbonic  acid,  and 
see  the  formation  of  alcohol  begin  there  immediately. 
Can  it  be  a  question  of  decay  in  this  quick  experiment 


212  pasteur:  the  history  of  a  mind 

when  the  fruits  come  out  of  their  matrass  healthy, 
of  good  flavor  and  sometimes,  as  in  the  case  of  prunes, 
more  firm  than  when  they  entered?  Do  you  not  know, 
furthermore,  that  M.  Muntz  has  made  the  same'  ex- 
periment on  entire  living  plants,  which  produce  alcohol 
when  made  to  live  for  some  time  in  carbonic  acid,  and 
which  resume  their  ordinary  existence,  when  restored 
to  the  air,  with  as  much  facility  as  a  traveller  who  comes 
out  of  a  tunnel  and  finds  once  more  the  air  and  sunshine  ?" 
And  thus  the  discussion,  which  I  have  made  a  dialogue, 
and  which  was  a  monologue,  might  have  been  continued 
a  long  time  without  bringing  forth  any  new  arguments 
or  elements  of  conviction,  for  the  experiments  of  Bernard 
were  too  vague  to  signify  anything,  and  Pasteur 
has  not  added  anything  new  to  this  point  of  the  discus- 
sion which  has  remained  sterile. 

It  was  the  same  with  a  lively  and  somewhat  passionate 
dialogue  which  took  place  between  Pasteur  and  Berthelot 
on  the  work  of  Bernard.  This,  however,  does  not  lack 
interest.  There  is  always  interest  in  a  strife  between 
men  of  this  stamp.  There  is  always  profit  in  hearing 
them  develop  their  arguments  and  discuss  the  ideas 
of  their  adversary.  But  here  the  opponents  were  not 
equal.  One  of  them  led  into  a  field  which  was  not  his 
own,  fenced  a  little  at  random,  and  sometimes  laid 
himself  open  to  a  thrust.  As  soon  as  he  left  the  least 
spot  unguarded,  the  blow  of  the  button  came  straight, 
promptly,  irresistibly.  It  was  truly  a  curious  passage 
at  arms,  but  as  it  did  not  bring  forth  any  new  facts,  its 
interest  has  disappeared.  Pasteur  came  out  of  it  more 
fixed  in  his  ideas,  and  Berthelot,  apparently,  without 
having  yielded  any  of  his.  This  should  lead  us  to 
distrust  all  discussions,  even  scientific  ones. 

It  is  a  common  belief  that  a  scientific  discussion  has 
a  greater  chance  of  coming  to  something  than  any  other, 


DISCUSSION  OF  THE  IDEAS  OF  CLAUDE  BERNARD      213 

because  it  takes  place  in  the  domain  of  facts.  But  a 
fact,  even  of  the  physical  order,  is  nothing  by  itself. 
It  becomes  something  only  when  it  passes  into  the  state 
of  an  intellectual  fact,  by  traversing  an  intelligence  the 
imprint  of  which  it  receives.  It  is  then  related  to  another 
fact,  sometimes  this  and  sometimes  that,  and  thus  are 
born  a  certain  number  of  conceptions  or  of  theories, 
which  make  more  or  less  proselytes.  There  are  certain 
facts,  or  certain  groups  of  facts,  on  which  tradition, 
habits  of  education  and  the  general  debility  of  intel- 
ligences have  set  everyone  in  accord,  and  which  are 
considered  as  verities,  as  belonging  to  the  foundations 
of  science,  until  the  day  when  an  investigator  more  bold 
than  others  thinks  of  taking  a  look  at  them,  and  con- 
tradicts them.  Then  they  disappear,  or  are  interpreted 
differently,  which  overthrows  the  accepted  theories. 

If  the  verities  of  the  rear-guard  are  so  subject  to 
caution,  what  must  be  the  case  with  those  of  the  advance 
guard,  those  which  are  the  recent  conquests?  For 
these  there  is  no  rule  and  tradition;  every  person  can 
interpret  them  according  to  his  liking.  Thus,  in  a 
discussion  with  Pasteur,  Frémy  had  had  on  this  subject 
an  idea  of  astonishing  candor.  He  proposed  to  his 
adversary  that  he  would  accept  all  his,  Pasteur's,  facts, 
provided  Pasteur  would  accept  all  his,  Frémy's,  inter- 
pretations. This  was  to  demand  everything,  for  we  do 
not  discuss  facts,  but  their  interpretations.  Whence 
it  results  that  even  a  serious  discussion  between  two  good 
minds  has  no  chance  of  leading  to  anything,  so  long  as  it 
remains  in  the  domain  of  facts  already  acquired.  It 
is  useful  only  when  it  leads  the  adversaries  to  investigate 
and  produce  something  new.  If  they  both  succeed, 
they  are  both  right,  even  when  they  are  not  in  agree- 
ment. If  they  do  not  venture,  or  if  neither  one  reaches 
any   results,    the   discussion   may   amuse  the    gallery, 


214  pasteur:  the  history  of  a  mind 


M 


instruct  it,  perhaps  even  give  rise  to  some  new  ideas 
there,  but  it  is  sterile  for  those  who  have  taken  part  in  it. 
A  savant  is  not  the  routine  man  of  the  study;  he  is  the 
man  of  the  laboratory. 


VII 
ORIGIN  OF  THE  YEASTS  OF  WINE 

Pasteur  had  entered  into  his  own  domain  in  the  dis- 
cussion of  a  part  of  the  posthumous  work  of  Bernard. 
He  wished  to  elucidate  a  question  which  he  had  had 
at  heart  since  the  beginning  of  his  studies  on  alcoholic 
fermentation,  to  which  he  has  returned  many  times, 
but  which  he  has  not  completely  solved,  because  it  is 
difficult.     That  is  the  question  of  the  origin  of  yeasts. 

In  his  Études  sur  la  bière,  he  had  very  much  enlarged 
the  conclusions  of  his  first  memoir  of  1862,  published 
in  the  Bulletin  de  la  société  chimique,  and  had  shown 
that  there  existed  a  great  number  of  yeasts,  different 
not  only  in  form,  but  also  in  their  physiological  prop- 
erties and  in  the  various  tastes  which  they  communicate 
to  the  liquids  which  they  ferment.  But  whence  come 
these  numerous  yeasts?  Are  they  special  vegetative 
forms  of  a  microscopic  plant  other  than  the  yeast,  and 
known  under  another  name?  And  if  so,  what  is  this 
plant?  or  rather,  what  are  the  different  plants  which 
give  birth  to  the  different  yeasts?  If,  on  the  contrary 
these  yeasts  have  no  other  form  of  reproduction  than 
that  with  which  we  are  familiar,  how,  in  nature,  do  they 
pass  the  winter  and  the  periods  during  which  there  are 
no  sugary  solutions  to  ferment?  Experiment  teaches, 
as  a  matter  of  fact,  that,  when  dried  and  exposed  to  the 
air,  the  various  yeasts  rapidly  lose  their  vitality.  . 


ORIGIN   OF  THE   YEASTS   OF   WINE  215 

The  question  does  not  arise  regarding  the  cultivated 
yeasts,  those  for  example  which  the  brewer  transfers 
from  vat  to  vat  in  all  seasons,  as  has  been  the  custom 
for  centuries,  but  applies  only  to  the  wild  yeasts,  which 
reappear  at  the  appointed  place  every  year,  to  ferment 
the  grape  crop.     For  the  wine-manufacturer  does  not 


Fig.  18. — Top  yeast  of  the  brewery. 
Old.  Rejuvenated. 

add  yeast  to  his  casks,  and  yet  the  ordinary  fermentation 
begins  freely  and  actively,  sometimes  in  24  hours.  At 
what  moment  do  the  stems  of  the  cluster  and  the  newly 
formed  fruits  become  charged  with  these  germs? 

Experiment  has  shown  that  this  occurs  late  in  the 
season.     As  long  as  the  grape  is  in  the  stage  of  verjuice 


216  pasteur:  the  history  of  a  mind 

which,  in  the  Jura,  is  toward  the  end  of  July,  we  can 
introduce  into  a  fermentable  juice  bits  of  the  fruit  and 
fragments  of  the  stem  of  the  cluster  without  any  fermen- 
tation of  this  juice,  provided  we  work  carefully  and 
avoid  every  chance  of  the  introduction  of  germs  other 
than  those  which  we  wish  to  study.  But,  as  the  grape 
ripens  and  the  day  of  the  harvest  approaches,  there  is 
an  increase  in  the  number  of  grapes  and  fragments  of 
the  stem  which  carry  the  yeasts  with  them  into  the  juice 
in  which  they  are  sown.  The  wood  of  the  cluster  is  at 
this  time  more  charged  with  germs  than  the  fruit,  which 
is,  itself,  more  richly  supplied  than  the  wood  of  the 
branch  or  the  twigs  of  the  vine.  Even  at  the  moment 
of  the  harvest,  not  all  the  grapes  are  carriers  of  germs 
capable  of  fermenting  them,  and  one  may  crush  them 
individually  and  even  by  twos  in  sterile  flasks,  that  is 
to  say,  place  their  superficial  pellicle  in  contact  with 
their  juice  without  seeing  the  latter  ferment.  Then, 
after  the  harvest,  when  we  have  made  it  by  collecting 
only  the  grapes,  leaving  behind  the  stem  of  the  cluster, 
the  germs  of  yeast  upon  the  latter  gradually  become  fewer 
and  fewer,  so  that  by  December  and  throughout  the 
winter  there  are  none  at  all.  There  remain  on  it  only  the 
germs  of  molds. 

This  first  question  when  solved  gave  rise  to  another. 
In  what  state,  on  the  surface  of  the  berry  and  on  the  wood 
of  the  stem,  do  we  find  these  germs  of  yeast,  the  existence 
of  which  we  have  just  demonstrated?  Washing  these 
surfaces  with  a  clean  badger's-hair  brush,  we  obtain  a 
clouded  drop  which,  under  the  microscope,  shows  nothing 
resembling  yeast.  We  see  there  only  numbers  of 
corpuscles  (A,  B,  Fig.  19)  of  a  more  or  less  deep  brown 
color  or  reddish  yellow  color,  with  thick  and  opaque 
walls,  and  other  more  translucent  cells,  none  of  which 
give  the  idea  or  present  the  aspect  of  the  familiar  yeasts. 


ORIGIN   OF   THE   YEASTS   OF   WINE 


217 


But  let  us  leave  this  dust,  evidently  living,  in  a  thin 
layer  of  sugar  solution  exposed  to  the  air  under  the  micro- 
scope, and  we  shall  see  come  forth  in  profusion  from 
certain  groups  of  the  brown  corpuscles,  cells  (Ai,  A2, 
Bi,  B2,  Fig.  19)  or  branching  filaments  which  at  once 
bud  and  segment  into  cells.  Now  these  cells  are  yeast 
cells,  for,  once  rejuvenated  in  contact  with  air  and  sown 
in  a  sweet  must,  they  produce  in  some  hours  an  active 
alcoholic  fermentation. 

Pasteur  must  have  felt  a  profound  joy  in  discovering 


B  B. 


Fig.  19. — Thick-walled  brown  cells  that  give  rise  to  wine  yeasts. 


these  facts,  for,  with  his  usual  perspicacity,  he  must 
have  seen  immediately  the  solution  of  a  problem  which 
had  been  in  his  mind  for  a  long  time,  and  of  which 
he  had  many  times  tried  in  vain  to  find  the  solution. 
The  origin  of  this  difficulty  was  the  experiment  of  Gay- 
Lussac  which  we  have  described,  and  in  which  this  scien- 
tist had  seen  some  bubbles  of  oxygen  produce  fermen- 
tation in  the  juice  of  grapes  crushed  in  a  test-tube  under 
mercury  and  remaining  inert  up  to  that  time. 

It  is  here  that  we  can  find  a  proof  of  the  truth  of  that 


218  pasteur:  the  history  of  a  mind 

which  I  have  affirmed  above.  Here  is  a  fact:  fermen- 
tation takes  place.  All  the  world  accepts  it,  but  how 
interpret  it?  The  proof  that  this  is  not  easy,  is  the  fact 
that  it  has  received  four  different  interpretations,  namely, 
one  by  Gay-Lussac,  one  by  Liebig  and  two  by  Pasteur. 

Gay-Lussac  was  content  to  say:  "It  is  the  oxygen 
which  sets  the  fermentation  going."  Liebig,  after  him, 
had  searched  more  profoundly  and  said:  "It  is  the  albu- 
minoid matter  of  the  must  which  needs  oxygen  in  order 
to  enter  into  decomposition  and  to  acquire  the  proper- 
ties of  a  ferment."  For  30  years  this  interpretation 
had  enjoyed  the  honors  and  credit  of  a  demonstrated 
truth.  Pasteur  arrives  on  the  scene  and  says:  "The 
albuminoid  matter  has  nothing  to  do  with  the  phenom- 
enon. The  ferment  is  a  living  organism  which  comes 
from  a  germ,  and  if  the  air  has  conveyed  into  our  test- 
tube  a  cause  of  fermentation,  it  is  because  it  has 
brought  a  germ  there." 

It  was  surely  not  without  some  regret  that  he  came 
to  this  conclusion,  because  this  view  furnished  a  weapon 
to  the  partisans  of  spontaneous  generation,  and  per- 
mitted them  to  say:  "How  is  this?  Do  you  admit  the 
germ  of  a  ferment  in  each  bubble  of  air?  Then  what 
becomes  of  your  conclusions  relative  to  the  rarity  of 
germs  in  the  atmosphere?"  This  objection  embarrassed 
him  only  a  little;  but  if  he  had  had  a  discussion  to  support 
on  this  subject  he  would  only  have  been  able  to  multiply 
words  upon  it.  He  must  have  uttered  a  cry  of  joy  when 
he  was  led  by  experiment  to  a  fourth  interpretation: 
The  germs  of  the  yeast  are  carried  by  the  grape-berry; 
they  are  inert  as  long  as  they  are  deprived  of  oxygen 
and  it  is  the  introduction  of  the  bubble  of  gas  which 
gives  the  whipstroke  of  departure  for  existence  in  a  state 
of  fermentation. 

It  is  a  singular  thing  that  all  these  results,  so  curious 


ORIGIN   OF   THE    YEASTS    OF   WINE  219 

and  so  new,  known  for  a  year  through  the  publication 
of  the  Études  sur  la  bière,  had  been  forgotten  in  1877  by 
Claude  Bernard.  One  of  his  principal  experiments  at 
St.  Julien,  which  he  had  repeated  at  various  times 
because  he  had  never  been  content  with  the  results,  had 
consisted  in  crushing  ripe  grapes,  sound  or  decayed,  to 
express  and  filter  therefrom  the  juice  until  it  was  per- 
fectly clear,  then  to  compare  in  an  approximate  manner 
the  quantity  of  alcohol  in  the  liquids  after  their  filtration, 
and  in  the  same  liquids  after  standing  about  48  hours. 
Bernard  found  that  in  this  interval  the  amount  of  alcohol 
increased,  although  the  liquid  remained  clear,  and  he  did 
not  hesitate  to  draw  from  this  fact  conclusions  favorable 
to  the  existence  of  the  diastase  of  which  we  have  al- 
ready spoken. 

The  experiment  of  Bernard  allowed  various  sources 
of  error  which  Pasteur  pointed  out  in  the  discussion 
which  he  made  of  it.  He  cites  in  opposition  the  results 
described  in  the  Études  sur  la  bière,  but  he  goes  farther: 
he  proposes  to  repeat  the  same  experiments  on  a  much 
larger  scale,  in  such  a  way  as  not  to  allow  any  of  those 
conditions  of  time  and  place  of  the  experiments  of  Ber- 
nard, which  one  could  invoke  in  their  favor,  to  come 
into  play.  Here,  we  can  let  him  speak,  for  he  has  him- 
self given  an  account  quite  at  length  of  this  episode, 
wherein  he  has  painted  a  very  exact  portrait  of  himself, 
with  his  ardor  in  returning  to  already  conquered  posi- 
tions when  they  were  menaced,  and  that  suddenness 
which  he  always  brought  into  his  decisions  when  a 
great  question  was  under  consideration. 

The  day  following  the  posthumous  publication  of  the 
manuscript  of  Bernard,  Pasteur's  plan  and  program  were 
made  :    '  '  Without  too  much  care  for  expense,  " 1  he  said,  '  '  I 

1  Examen  critique  d'  un  écrit  posthume  de  Cl.  Bernard  sur  la  fermenta- 
tion, p.  66. 


220  pasteur:  the  history  of  a  mind 

ordered  in  all  haste  several  hothouses  with  the  intention 
of  transporting  them  into  the  Jura,  where  I  possess  a 
vineyard  some  dozens  of  square  meters  in  size.  There 
was  not  a  moment  to  lose.     And  this  is  why! 

"I  have  shown,  in  a  chapter  of  my  Études  sur  la  bière, 
that  germs  of  yeast  are  not  yet  present  on  the  grape 
berry  in  the  state  of  verjuice,  which,  in  the  Jura,  is  at 
the  end  of  July.  We  are,  I  said  to  myself,  at  a  time  of 
year  when,  thanks  to  a  delay  in  growth  due  to  a  cold 
rainy  season,  the  grapes  are  just  in  this  state  of  verjuice 
in  the  canton  of  Arbois.  By  taking  this  moment  to 
cover  some  vines  with  hothouses  almost  hermetically 
closed,  I  would  have  in  October  during  the  grape  har- 
vest, vines  bearing  ripe  grapes  without  any  yeasts  of 
wine  on  the  surface.  These  grapes,  being  crushed  with 
the  precautions  necessary  not  to  introduce  germs  of 
yeast,  will  be  able  neither  to  ferment  nor  to  make  wine. 
I  shall  give  myself  the  pleasure  of  taking  them  to  Paris, 
of  presenting  them  to  the  Academy,  and  of  offering  some 
clusters  to  those  of  my  confrères  who  may  still  believe 
in  the  spontaneous  generation  of  yeast. 

"The  fourth  of  August,  1878,  my  hothouses  were 
finished  and  ready  to  be  put  up.  The  work  of  setting\ip 
and  of  putting  in  the  glass  was  finished  in  a  few  days. 

"  During  and  after  the  installation  of  the  hothouses, 
I  searched  with  care  to  see  if  the  germs  of  yeast  were 
really  absent  from  the  clusters  in  the  state  of  verjuice, 
as  I  had  found  hitherto  to  be  the  case.  The  result  was 
what  I  expected;  in  a  great  number  of  experiments  I 
determined  that  the  verjuices  of  the  vines  in  the  canton 
of  Arbois  and  notably  those  of  the  vines  covered  by  the 
hothouses,  bore  no  trace  of  germs  of  yeast  at  the  beginning 
of  the  month  of  August,  1878." 

"In  the  fear  that  an  insufficient  sealing  of  the  hot- 
houses would  allow  the  germs  to  reach  the  clusters,  I 


ORIGIN    OF   THE    YEASTS   OF   WINE  221 

took  the  precaution,  while  leaving  some  of  the  clusters 
free,  to  cover  a  certain  number  on  each  vine  with  cot- 
ton which  had  been  brought  to  a  temperature  of  about 
150°C." 

".  .  .  Toward  the  tenth  of  October,  the  grapes  in  the 
hothouses  were  ripe;  through  the  skin  of  the  berry,  one 
could  clearly  distinguish  the  seeds,  and  in  taste  they  were 
as  sweet  as  the  majority  of  the  grapes  grown  outside  ; 
only,  under  the  cotton,  the  grapes,  naturally  black,  were 
scarcely  colored,  rather  violaceous  than  black,  and  the 
white  grapes  had  not  the  golden  yellow  tint  of  white 
grapes  exposed  to  the  sun.  Nevertheless,  I  repeat,  the 
maturity  of  both  left  nothing  to  be  desired. 

"On  the  tenth  of  October,  I  made  my  first  experiment 
on  the  grapes  of  the  uncovered  clusters  and  on  those 
covered  with  the  cotton,  comparing  them  with  some  which 
had  grown  outside.  The  result  I  may  say  surpassed 
my  expectation.  . . .  To-day,  after  a  multitude  of  trials, 
I  am  just  where  I  ,started,  that  is  to  say,  it  has  been 
impossible  for  me  to  obtain  a  single  time  the  alcoholic 
yeast  fermentation  from  clusters  covered  with  cotton, 
and  as  for  the  uncovered  clusters  of  the  same  vines  I 
have  had  only  a  single  case  of  fermentation,  by  a  yeast 
which  I  described  a  long  time  ago  in  the  Bulletin  de  la 
Société  chimique,  and  which  has  since  received  from  Dr. 
Reess  the  name  of  Levure  apiculée. 

"A  comparative  experiment  naturally  suggested  it- 
self. When  the  hothouses  were  set  up  we  were  in  the  first 
period,  that  in  which  the  germs  are  absent  from  the 
stem  and  the  clusters.  At  the  time  when  the  experiments 
which  I  have  just  described  took  place,  from  the  10th  to 
the  31st  of  October,  we  were,  on  the  contrary,  in  the 
period  when  the  germs  were  present.  It  was  then  pre- 
sumable that  if  I  detached  hothouse  clusters  covered 
with  cotton  and  exposed  them,  after  removing  the  cot- 


222  pasteur:  the  history  of  a  mind 

ton,  on  the  branches  of  vines  in  the  open,  these  clusters 
which  up  to  this  time  could  not  enter  into  fermentation 
after  the  crushing  of  their  berries,  would  ferment  under 
the  influence  of  the  germs  which  they  could  not  fail  to 
receive  in  their  new  position.  This  was  precisely  the 
result  which  I  obtained." 

It  is  clear  that  in  the  presence  of  these  results,  nothing 
was  left  of  the  mediocre  experiments  of  Bernard.  It 
was  certain  that  the  germs  of  the  yeast  were  brought 
periodically  to  the  vine  by  an  external  plant,  on  the  nature 
of  which  Pasteur  could  make  only  some  plausible  hy- 
potheses, and  furthermore,  on  which  we  are  not  yet  exactly 
informed.  If  I  have  dwelt  so  long  on  this  last  demon- 
stration of  Pasteur,  it  is  not  simply  to  consolidate  an 
already  established  proof,  but  to  show,  by  an  example 
which  seems  to  me  typical,  how  Pasteur  was  able  to 
broaden  the  problems  which  he  approached. 

The  problem  which  he  had  placed  before  himself  in 
the  preceding  experiments  was  apparently  very  limited: 
it  was  the  origin  of  yeasts.     Behold  how  he  enlarged  it: 

"May  I  be  permitted,"  he  continued  immediately 
after  having  written  the  lines  which  precede,  "to  enter 
here  into  an  experimental  digression,  very  worthy  of 
interest?  I  have  said  that  the  clusters  of  ripe  grapes 
carry  on  their  surface  the  germs  of  ferments  which  pro- 
duce the  wine  in  the  vat  and  in  the  casks  of  the  vine 
grower.  Consequently,  is  it  not  probable  that  at  the 
time  of  the  harvest  the  rains  may  collect  many  of  these 
germs  and  spread  them  over  the  soil  of  the  vineyard? 
Experiment  confirms  these  suppositions.  Having  de- 
posited very  small  quantities  of  earth  from  a  vineyard 
in  a  series  of  tubes  which  contain  the  must  of  grapes 
sterilized  by  a  preliminary  boiling,  I  have  seen  this  must 
undergo  alcoholic  fermentation  in  many  of  the  tubes 
of  each  series.    Without  injuring  the  success  of  the 


OEIGIN   OF   THE    YEASTS   OF   WINE  223 

experiment  we  may  take  these  samples  of  earth  at  a 
considerable  distance  from  the  surface,  even  from  a  depth 
of  10  to  15  centimeters.  Still  more  frequent  in  this 
kind  of  experiment,  is  the  alcoholic  fermentation  by 
yeasts  of  the  genus  Mucor,  so  abundant  in  cultivated 
soil  are  the  spores  of  these  little  plants. 

"I  have  had  the  curiosity  to  compare  the  soil  of  the 
vineyard  and  that  covered  by  my  hothouses  with 
regard  to  the  presence  of  the  spores  of  grape  yeasts  and 
the  spores  of  Mucor.  But,  although  the  experiment 
has  been  made  a  great  number  of  times,  I  have  never 
seen  produced  in  my  tubes  with  the  soil  from  my 
hothouses,  the  alcoholic  fermentation  due  to  the  alcoholic 
yeasts  of  the  grape;  very  frequently  there  appears, 
on  the  contrary,  the  fermentation  due  to  the  yeast  of  the 
Mucor. 

"How  many  reflections  these  results  lead  to  !    Can  we 
fail  to  observe  that  the  further  we  penetrate  into  the 
experimental  study  of  germs,  the  more  we  see  therein 
unexpected  lights  and  just  ideas  leading  to  knowledge 
of  the  causes  of  contagious  diseases!    Is  it  not  worthy 
of  attention  that  in  this  vineyard  of  Arbois,  and  this 
would  be  true  of  the  millions  of  hectares  of  vineyards 
all  over  the  world,  there  was  not,  at  the  time  when  I 
made  these  experiments  which  I  have  just  described, 
a  particle  of  soil,  so  to  speak,  which  was  not  capable 
of  provoking  the  vinous  fermentation,  and  that,  on  the 
contrary,  the  soil  of  the  hothouses  of  which  I  have  spoken 
was  unable  to  do  this.     And  why?    Because,  at  a  defi- 
nite moment,  I  covered  this  soil  with  some  glass.     The 
death,  if  I  dare  to  speak  thus,  of  a  grape  berry  which 
has  been  thrown  on  the  ground  of  any  vineyard,  will 
be,  somehow  or  other,  infallibly  accomplished  by  the 
yeast  parasites  of  which  I  speak;  but  this  kind  of  death 
will  be  impossible,  on  the  contrary,  in  the  little  corner 


224  pasteur:  the  history  of  a  mind 

of  soil  which  my  hothouses  cover.  These  few  cubic 
meters  of  air,  these  few  square  meters  of  the  surface 
of  the  soil  were  there  in  the  midst  of  a  possibly  universal 
contagion,  and  they  withstood  it  for  a  period  of  many 
months.  But  of  what  service  would  the  shelter  of  the 
hothouses  be  in  the  case  of  disease  and  death  caused  by 
the  Mucor  parasites?  Not  the  least!  Since  the  para- 
sites of  the  saccharomyces  reach  the  surface  of  the  grapes 
at  a  definite  period  of  the  year,  a  shelter,  put  on  in  time, 
was  able  to  keep  them  free  from  these  germs,  as  Europe 
is  protected  from  the  cholera  and  the  plague  by  quaran- 
tines. The  Mucor  parasites,  on  the  contrary,  being 
present  during  the  whole  year  in  the  soil  of  our  fields 
and  our  vineyards,  were  necessarily  under  the  hothouses 
when  they  were  put  up,  like,  in  some  respects,  the  germs 
of  our  common  contagious  diseases,  against  which  the 
quarantines  opposed  to  cholera,  yellow  fever,  or  the 
plague  are  ineffectual. 

"Must  we  not  believe,  by  analogy,  that  a  day  will 
come  when  preventive  measures,  of  easy  application, 
will  arrest  these  plagues  which  at  one  blow  desolate 
and  terrify  whole  populations,  as  did  the  yellow  fever 
in  its  recent  invasion  of  the  Sénégal  and  the  valley  of 
the  Mississippi,  or  the  bubonic  plague  which  has  raged 
on  the  shores  of  the  Volga." 

These  few  lines  form  the  introduction  to  a  new  life. 
They  show  the  preoccupations  which  had  just  taken 
possession  of  Pasteur's  mind  and  which  already  com- 
pletely filled  it.  They  were  written  in  1879,  when  the 
studies  of  anthrax  and  of  chicken  cholera  were  already 
begun.  They  form  the  connecting  link  between  the 
old  labors  and  the  new,  and  it  is  for  this  reason  that  I 
have  transcribed  them.  I  should  be  very  much  aston- 
ished if  the  reader  has  not  noted  their  resolute  manner 
of  expression  and  their  prophetic  tone. 


SEVENTH  PART 
Studies  on  the  Etiology  of  Microbial  Diseases 

I 
THE  IDEAS  ON  CONTAGION  PRIOR  TO  1866 

We  have  reached  the  period  when  Pasteur,  who  had 
his  eyes  fixed  for  a  long  time  upon  the  promised  land 
of  pathology,  was  going  finally  to  be  able  to  enter  it.  He 
was  ripe  for  this  work,  and  provided  with  the  necessary 
technical  outfit  to  undertake  it.  His  laboratory  was 
at  that  time  the  only  one  in  which  it  was  possible  to 
properly  handle  bacteria  and  be  certain  of  the  purity 
of  a  sowing  carried  through  an  indefinite  series  of  suc- 
cessive cultures.  While  elsewhere  every  one  was  strug- 
gling with  nutrient  liquids  of  mediocre  composition 
such  as  those  mineral  solutions  of  Pasteur  or  of  Cohn, 
which  have  played  so  many  tricks  with  Klebs  and  those 
who  made  use  of  them,  Pasteur  had  discarded  them  for 
a  long  time,  and  had  adopted  the  fertile  principle  of 
giving  to  each  bacterium  the  kind  of  medium  adapted 
to  it. 

It  was  following  the  beautiful  researches  of  Raulin 
that  he  had  understood  the  importance  of  this  question. 
He  had  reflected  for  a  long  time  and  he  called  the  atten- 
tion of  his  pupils  frequently  to  the  fact  that  when 
cultivated  upon  its  favorite  medium,  the  discovery  of 
which  had  given  Raulin  so  much  trouble,  Aspergillus 
niger  defends  itself  unaided  and  successfully  against  the 
intervention  of  every  parasite.  While  one  is  obliged 
to  operate  protected  from  the  germs  of  the  air  and  in 

15  225 


226  pasteur:  the  history  of  a  mind 

flamed  flasks,  when  he  wishes  to  cultivate  and  keep  pure 
a  'species  the  condition  for  the  development  of  which 
he  knows  only  imperfectly,  Aspergillus  niger  gives 
admirable  cultures,  flourishing  and  pure,  in  contact  with 
the  air,  and  in  liquids  and  flasks  which  one  has  not  taken 
the  trouble  to  sterilize.  Consequently,  in  the  presence  of 
every  new  species,  his  first  care  was  to  try  several  culture 
media  so  as  to  find  that  which  suited  it  the  best. 

Having  this  principle  of  culture  in  the  most  favorable 
medium,  Pasteur  was  also  the  only  one  who  had  the 
ability  to  add  a  proper  technique.  This  was  due  especially, 
as  we  have  seen,  to  the  efforts  of  his  assistants  :  Joubert, 
Chamberland  and  Roux. 

Finally,  as  a  last  advantage,  Pasteur  had  that  of  being 
20  years  old  in  the  study  of  microbes  and  of  having  more 
complete  notions  about  them,  their  needs,  their  physi- 
ology and  their  morphology,  than  any  of  the  scientific 
men  of  his  time.  It  was  because  of  this  that  he  was 
able  so  quickly  to  catch  up  with  and  soon  to  distance 
those  who  had  entered  before  him  on  this  pathway, 
for  at  the  time  when  he  first  took  up  the  study  of  anthrax 
in  1876,  there  had  been  already  several  pathogenic  mi- 
crobes discovered,  and  Koch  had  just  published  his 
famous  work  on  the  spore  of  the  anthrax  bacteridium. 

To  appreciate  thoroughly  the  rôle  and  the  part  of 
Pasteur  in  this  great  question  of  pathology,  one  must 
know  the  general  state  of  science  and  of  the  scientific 
mind  in  1876. x  That  is  not  as  easy  as  one  might  believe 
it  to  be,  considering  that  we  have  to  go  back  only  a  few 
years.  The  ideas  which  had  currency  in  1840  and  even 
in  1860  on  the  subject  of  contagious  diseases  are  so  far 
removed  from  our  own  that  they  have  almost  the  dis- 

1  One  may  obtain  a  very  good  idea  of  what  it  was  in  Germany  by 
reading  Nâgeli's  Die  Niederen  Pilze  in  ihren  Beziehungen  zu  den  Infec- 
tionskrankheiten  und  der  Gesundheitspflege,  Munich,  1877.     TVs. 


THE  IDEAS  ON  CONTAGION  PRIOR  TO  1866    227 

tance  of  centuries.  One  finds  the  same  trouble  in  assim- 
ilating them  that  he  would  if  they  were  some  philo- 
sophical work  of  the  middle  ages,  and  therein  we  see  very 
well  what  a  chimera  is  the  history  of  scientific  ideas. 
In  order  to  understand  the  past  state  of  a  question,  it 
is  necessary  to  assume  an  artificial  state  of  mind,  to  pass 
the  sponge  over  certain  ideas  which  we  believe  to  be 
true,  putting  in  their  place  others  which  we  know  to  be 
false,  in  brief,  to  change  the  state  of  one's  brain,  and 
that  is  impossible. 

I  know  very  well  that  there  remain  in  the  books  of 
the  period  words  which  are  supposed  to  be  the  clothing 
of  ideas,  and  through  which  one  may  try  to  see  what 
they  covered.  The  partisans  of  the  history  of  science 
tell  us,  when  it  is  a  question  of  mathematics  or  physics 
or  of  natural  history,  that  these  words  have  a  more 
precise  meaning  than  when  it  is  a  question  of  philosophy, 
and  they  are  right.  But  if  they  conclude  therefrom  that 
the  history  of  science  is  easy  to  write,  or  even  possible, 
they  are  wrong,  for,  even  in  science  homonyms  are  not 
synonyms  30  years  apart.  The  same  tinsels  cover  very 
different  small  rough  models.  We  have  just  here  a 
striking  example  of  this  fact. 

For  example,  the  words  contagium  vivum  or  animatum 
have  been  current  in  science  for  a  long  time.  They 
have  been  found  in  Varro  and  Columella.  Acknow- 
ledging that  they  may  still  serve  to  express  the  ideas  of 
to-day,  one  has  sometimes  concluded  that  these  ideas 
are  very  old,  that  only  knowledge  of  the  mode  of  con- 
tagion has  been  perfected  with  progress  of  time,  and 
that  Pasteur  is  only  the  last  one  come,  and  the  most 
powerful,  of  a  series  of  investigators  who  have  labored 
with  the  same  directive  idea. 

I  have  no  need  to  go  back  very  far  to  demonstrate  the 
inexactness  of  this  point  of  view.     I  will  confine  myself 


228  pasteur:  the  history  of  a  mind 

to  the  scientific  man  whom  one  most  willingly  cites  as 
the  immediate  precursor  of  Pasteur,  to  Henle  who, 
about  1840,  published  a  sort  of  theory  of  disease,  the 
developments  of  which  seem  in  fact  in  harmony  with 
our  present  ideas.  For  Henle,  the  evolution  of  a  disease 
is  in  all  respects  comparable  to  that  of  a  living  being. 
The  quantity  of  morbid  matter  which  may  produce  it  in 
a  healthy  individual,  like  the  seed  of  the  plant  or  animal, 
is  out  of  all  weighable  proportion  to  the  quantity  of  effect 
produced,  and  to  the  quantity  of  morbid  matter  which 
the  diseased  individual  produces  in  his  turn.  An  acorn 
produces  an  oak,  which  yields  in  its  turn  a  multitude 
of  acorns. 

So  much  for  a  first  point  of  view.  Here  is  a  second  : 
Between  the  time  when  the  morbid  matter  enters  into 
the  body,  and  that  in  which  it  is  translated  into  dis- 
orders preceding  disease,  a  period  intervenes  which  is 
well  known  under  the  name  of  period  of  incubation,  which 
is  nearly  constant  for  each  disease,  and  differs  from  one 
disease  to  another.  How  is  it  possible  not  to  connect 
it  with  the  duration  necessary  for  the  development  of 
the  germ  and  the  infection  of  the  tissues?  How  explain 
it  otherwise  than  by  the  doctrine  of  parasitism?  So 
long  as  the  disease  lasts,  he  who  has  it  must  be  a  source 
of  contagium.  When  it  has  ceased,  all  danger  of  conta- 
gion ceases.  This  means  that  the  germ  is  dead  and  can 
no  longer  injure.  The  same  for  epidemics.  In  their 
appearance,  their  extension  over  a  territory  more  or  less 
great,  their  lingering  termination,  do  they  not  resemble 
absolutely  the  beginning,  the  middle  and  the  end  of  a  veg- 
etation, and  is  it  not  remarkable  also  that  many  disin- 
fectants and  even  remedies  should  be  at  the  same  time 
active  agents  of  destruction  of  vegetable  or  animal  life? 

Behold,  it  has  been  said,  an  unlettered  print  of  the 
system  of  Pasteur,  and  that  which  makes  still  further 


THE    IDEAS   ON   CONTAGION   PRIOR   TO    1866         229 

for  the  perspicacity  of  Henle  is  that  he  pointed  out  the 
bacteria  as  among  the  beings  capable  of  giving  infectious 
germs,  and  that  he  thus  foresaw  and  almost  enunciated 
our  present  day  ideas.  I  reply,  you  forget  a  detail 
which  is  far  from  being  insignificant.  For  Henle,  the 
germ  of  the  disease  was  not  something  superposed  upon 
the  sick  person  and  independent  of  him,  it  was  something 
belonging  to  him,  borrowing  from  him  a  sort  of  patho- 
logical vitality,  and  able  to  transport  it  elsewhere. 
The  system  of  Henle  is  much  more  in  consonance  with 
what  one  then  knew  of  viruses,  of  the  transmission  of 
smallpox,  of  vaccine,  than  with  what  one  had  recently 
learned  of  the  transmission  of  itch  or  of  muscardine,  and 
we  find  therein  nothing  of  the  new  idea  brought  by 
Pasteur  concerning  the  living  virus,  which  can  be 
cultivated  and  modified  outside  of  the  organism. 

A  physician  of  La  Teste,  J.  Hameau,  had  entered  upon 
a  better  pathway  in  a  paper  which,  written  in  1836, 
was  unfortunately  not  published  until  1847,  a  long  time 
after  the  work  of  Henle.  Hameau,  contrary  to  Henle, 
had  taken  the  itch  especially  as  the  point  of  departure 
for  his  deductions  and  for  his  system,  and  all  that  which 
is  in  accord  with  this  premise  is  correct  for  he  had  truly 
method  and  logic  in  his  mind.  On  the  contrary  he  wan- 
ders when  he  takes  up  the  question  of  miasms,  to  which 
he  attaches  dysentery,  erysipelas,  and  hospital  gangrene. 
For  him,  there  was  not  in  these  cases  any  contagium 
vivum,  while  there  was  such  for  Henle,  and  that  shows  us 
how  necessary  it  is  to  distrust  words,  and  how  much  one 
would  have  disturbed  both  Henle  and  Hameau  by  placing 
them  in  the  same  camp,  under  the  pretext  that  they  had 
the  same  words  inscribed  upon  their  banner. 

It  is  not  these  philosophical  speculations  which  cause 
science  to  advance.  We  must  be  grateful  to  all  of  those 
from  Columella  and  Varro,  by  way  of  Paracelsus,  Fra- 


230  pasteur:  the  history  of  a  mind 

castoro  and  Linnaeus,  who  have  outstripped  their  epoch 
by  showing  with  more  and  more  precision  the  evident 
analogies  between  the  phenomena  of  fermentation  and 
of  diseases,  and  who  have  more  or  less  suspected  living 
organisms  in  diseases  in  proportion  as  they  appeared  in 
fermentations.  But  it  is  not  in  these  multicolored 
big  lanterns  moving  about  in  the  night  that  we  are  to 
see  the  dawn  of  our  present  ideas. 


II 

CAUSES  OF  THE  STERILITY  OF  THE  IDEAS  UPON 
CONTAGION 

Such  being  the  case,  what  one  has  the  right  to  ask  is 
why  these  ideas  did  not  attract  the  attention  of  con- 
temporaries to  a  greater  extent.  Why  have  systems  as 
suggestive  as  those  of  Henle,  of  Hameau,  remained 
unknown  or  disdained?  We  shall  here  find  the  secret 
of  their  weakness.  It  is  because  they  were  works  of 
the  closet  and  because  not  being  developed  from  experi- 
ment, they  did  not  end  in  experiment.  Systematic 
and  brilliant  minds  have  never  been  wanting  in  medi- 
cine. When  Hameau  was  writing,  Broussais  was  still 
alive:  the  cloud  of  dust  which  he  had  raised,  and  in  the 
midst  of  which  his  disciples  were  felicitating  themselves, 
was  too  thick  for  the  vague  light  of  the  little  physician 
of  La  Teste,  who  explained  very  well  certain  known 
facts,  but  did  not  point  out  new  pathways. 

In  1840,  at  the  moment  of  the  appearance  of  the  mem- 
oir of  Henle,  the  German  physicians  had,  on  their  side, 
better  excuses  than  those  of  to-day  for  not  paying  atten- 
tion to  these  new  ideas.  They  were  too  much  in  oppo- 
sition to  the  strong  and  fertile  conceptions  that  Vir- 
chow  was  introducing  at  this  time  into  the  science. 


THE  STERILITY  OF  THE  IDEAS  UPON  CONTAGION      231 

Without  doubt  it  must  be  admitted  that  certain  skin 
diseases  like  favus,  herpes  tonsurans,  thrush,  and  itch 
could  be  produced  by  animals  or  vegetables.  But  of 
what  importance  were  these  maladies  when  placed  by 
the  side  of  the  infectious  diseases  in  which  one  found 
nothing  comparable?  Now  cellular  pathology  explained 
the  latter  by  the  famous  principles  of  heterotopy  and 
heterochronia.  Every  pathological  modification  was  for 
it  only  a  physiological  transformation  displaced  in  time 
or  place,  developing  itself  in  an  organ  which  could  not 
endure  it,  or  at  a  time  when  it  was  abnormal.  The 
secret  of  the  disease  was,  therefore,  in  the  anatomy  of 
the  tissues,  which,  under  this  powerful  impulse,  multi- 
plied its  discoveries  and  took  in  all,  from  tumors  to 
viruses,  from  exostoses  to  exanthemata,  and  to  the  pus- 
tules of  smallpox  or  of  vaccine. 

The  idea  that  there  could  be  in  the  tissues  organisms 
come  from  the  exterior  which,  by  penetrating  and  de- 
veloping there,  impressed  upon  them  specific  modifi- 
cations, was  in  disagreement  with  the  general  current 
of  anatomical  ideas;  and  yet  more  with  physiological 
views.  At  this  moment  in  fact,  a  pleiad  of  illustrious 
scientific  men,  Helmholtz,  Du  Bois  Reymond,  Ludwig 
and  Brucke,  began  to  oppose  the  ancient  conception  of 
the  vital  force,  and  to  explain  all  physiological  phenom- 
ena of  the  living  being  by  forces  of  the  physico-chem- 
ical order.  It  was  the  same  idea  that  Liebig  followed, 
as  we  have  seen,  in  the  study  of  fermentations.  Into 
a  coterie  shining  with  such  names,  it  is  plain  with  what 
welcome  the  idea  would  be  received  of  the  interven- 
tion under  the  form  of  living  and  parasitic  organisms 
of  this  proscribed  and  everywhere  driven  out  vital  force. 

And  this  is  precisely  why  Pasteur  who  had  overthrown 
the  ideas  of  Liebig  respecting  fermentations,  found  it 
necessary  in  continuing  his  work  to  meet  and  overthrow 


232  pasteur:  the  history  of  a  mind 

the  ideas  of  Virchow  in  pathology.  If  Fate  had  willed 
that  he  should  not  finish  his  task,  that  he  should  suc- 
cumb to  the  hemiplegia  which  attacked  him  at  the  time 
of  his  studies  on  silkworms,  some  other  scientific  man 
would  have  come,  a  Koch  for  example,  for  whom  Pasteur 
would  have  been  a  precursor  because  he  would  have 
pointed  out  the  way  and  left  behind  him  the  means  of 
following  it.  His  pathological  work  was  the  develop- 
ment and  the  compliment  of  his  work  upon  the  fermen- 
tations. But  Pasteur  had  no  precursor  in  the  proper 
sense  of  this  word,  that  is  to  say,  he  did  not  develop 
and  extend  the  ideas  of  anyone  else.  He  remains  the 
equal  of  many  when  he  demonstrates  the  bacterial  origin 
of  anthrax  or  of  other  diseases.  Where  he  is  without 
equal  is  when  he  discovers  the  attenuation  of  viruses, 
and  when  he  introduces  into  science  that  fertile  no- 
tion which  allows  us  to  act  upon  a  disease  by  acting, 
not  upon  the  sick  person,  as  up  to  that  time  one  had 
been  in  the  habit  of  doing,  but  upon  the  pathological 
bacterium. 

What  renders  his  history  particularly  interesting  at 
this  period,  is  that  we  can  follow  the  stages  of  his 
progress.  As  we  have  seen,  he  had  had  for  a  long  time 
the  desire  to  enter  into  pathology.  He  was  led  to  it 
by  that  secret  force  of  things  the  elements  of  which  we 
have  just  analyzed.  He  showed  himself  an  eager  student 
of  medical  works  and  after  having  borrowed  from  them 
certain  words,  as  we  have  seen,  at  the  beginning  of  his 
studies  upon  the  disease  of  silkworms,  he  began  to  pene- 
trate into  things.  From  this  stage  his  choice  was  nar- 
rowly restricted.  He  had  read  and  meditated  on  the 
works  of  Jenner  upon  vaccine,  those  which  Coze 
and  Feltz  had  just  published.  But  what  interested  him 
most  of  all  were  the  studies  which  Davaine  was  pursuing 
at  this  time  upon  the  anthrax  bacteridium. 


anthrax:  pollender,  brauell,  delafond     233 

III 
ANTHRAX:  POLLENDER,  BRAUELL,  DELAFOND 

The  history  of  this  bacteridium  was  already  quite 
ancient;  it  began  in  1850.  It  was  at  this  time  that 
Rayer,  studying  at  Chartres  the  anthrax  of  horned 
cattle  with  the  aid  of  Davaine,  had  seen  it  in  the  form 
of  little  rods  in  the  blood  of  dead  animals  (Fig.  20), 
but  without  comprehending  its  importance.  In  1855, 
Pollender  had  seen  it  again,  had  noted,  like  Rayer,  the 
agglutinated  condition  of  the  red  blood-corpuscles  in 
the  anthrax  blood,  and  the  considerable  number  of 
leucocytes  which  were  observed  along  with  it.  In  addi- 
tion, by  reactions  under  the  microscope,  he  had  estab- 
lished that  the  little  rods  found  in  this  blood  were  not 
filaments  of  fibrin,  but  behaved  on  the  contrary  like 
vegetation.  The  principal  interest  of  his  communi- 
cation respecting  them  centers  in  the  fact  that  he  asked 
what  they  signified.  Are  they  the  infectious  matter 
itself?  Are  they  only  the  carriers  of  this  matter?  Or, 
have  they  nothing  to  do  with  it?  We  should  say  to-day: 
Are  they  the  infectious  agent,  do  they  convey  this  agent, 
or  is  it  necessary  to  seek  it  elsewhere?  This  is  the 
question  that  Pollender  asked  himself  with  much  per- 
spicacity, and  which  it  required  30  years  to  settle. 

Science  is  like  a  train  in  the  hands  of  a  crew,  which, 
after  having  gone  forward,  sometimes  goes  backward. 
Scarcely  had  Pollender  well  set  forth  the  question  than 
Brauell  befogged  it  by  confusing  the  bacteridia  of  an- 
thrax, considered  up  to  this  moment  as  sufficiently  spe- 
cific, with  the  harmless  bacteria  of  putrefaction,  which 
led  him  quite  naturally  to  discover  them  in  various 
diseases,  and  consequently  to  sever  them  from  anthrax. 
At  most  he  admits  that,  in  this  disease,  the  harmless 


234  pasteur:  the  history  op  a  mind 

bacteria  appear  in  the  blood  before  death  instead  of 
after  death  as  in  other  diseases. 

The  following  year  he  took  a  new  step  in  the  wrong 
direction.  He  stated  that  inoculation  with  the  blood 
of  a  horse  having  anthrax  had  caused  a  deadly  anthrax 
in  the  inoculated  animal,  although  this  blood  did  not 


Fig.  20. — Bacteridium  of  anthrax. 
In  artificial  cultures.  In  the  blood  of  a  diseased  animal. 

contain  bacteridia.  Evidently,  therefore,  these  little 
rods  were  neither  the  contagion  nor  the  carrier  of  the 
contagion  nor  even,  one  might  add,  the  necessary  com- 
panions of  it.  Brauell,  therefore,  undid  what  Pollender 
had  done.  Henceforth  the  little  rods  retained  only  a 
diagnostic  or  a  prognostic  value  in  certain  cases,  that  is  to 


anthrax:  pollender,  brauell,  delafond     235 

say,  the  animals  which  showed  them  in  their  blood 
during  life  had  anthrax  without  question,  and  were 
certain  to  die  in  the  near  future,  but  they  might  also 
die  of  anthrax  without  containing  the  bacteridia. 

The  reaction  against  these  retrograde  ideas  was  set 
on  foot  by  Delafond,  who  pointed  out  the  confusion 
made  by  Brauell  and  even  by  Pollender  between  the 
bacteridia  of  anthrax  and  the  harmless  bacteria  of  putre- 
faction: because  in  proportion  as  the  second  develop, 
the  first  disappear. 

Delafond  goes  further.  He  seeks  to  prove  the  vege- 
table nature  of  the  anthrax  bacteridia  by  subjecting 
them  to  culture  experiments.  He  exposed  the  anthrax 
blood  in  open  flasks  to  the  air  at  a  suitable  temperature. 
After  4  or  5  days,  the  short  rods  in  the  blood  had  in- 
creased and  doubled  or  tripled  their  length,  and  they 
quadrupled  or  quintupled  it  after  8  or  10  days.  This 
well  demonstrated  that  the  bacilli  were  living.  Delafond 
even  tried  to  push  the  growth  to  its  completion  to  see 
it  arrive,  as  he  says,  at  the  spore  or  seed.  These  words 
spore  and  seed  had  evidently  for  him  not  the  precise 
meaning  which  they  have  since  acquired,  but  they  do 
honor  to  his  perspicacity,  and  it  is  curious  to  see  them 
appear  in  connection  with  bacteridia,  in  a  memoir  of  1860. 

To  sum  up  then,  for  those  who  kept  au  courant  with 
the  question,  a  connection  between  the  bacteridia  of 
Rayer  and  the  development  of  the  disease  of  anthrax  or 
sang  de  rate,  although  still  obscure,  was  probable  from 
the  proofs  and  the  culture  experiments  of  Delafond. 
But  it  is  not  with  such  a  feeble  array  of  facts  that  an 
idea  can  enter  into  the  domain  of  science,  especially 
when  it  finds  therein  minds  prejudiced  against  it. 
"What  is  it  worth  to  us,"  one  might  have  said  at  this 
epoch,  "this  new  etiological  doctrine?  Is  there  not 
something   strange   about   it?    Can   one   imagine   the 


236  pasteur:  the  history  of  a  mind 

powerful  and  colossal  life  which  animates  a  horse  or 
an  ox,  threatened  and  destroyed  by  this  miserable  little 
rod  which  we  can  see  only  under  a  microscope?  This  rod 
appears,  moreover,  only  some  hours  before  death,  and 
when  the  animal  is  already  very  ill.  Where  is  it  and 
what  has  it  been  doing  earlier?  You  tell  us,  you  who 
believe  in  it,  that  it  does  not  long  survive  the  animal 
which  it  has  killed,  and  dies  when  the  tissues  decay. 
But  all  animals  dead  of  anthrax  decay,  for  we  bury 
them  quickly  without  making  any  use  of  them.  And, 
therefore,  how  do  you  explain  that  there  are  epidemics  of 
anthrax  every  year,  epidemics  which  appear  in  the  summer 
after  having  disappeared  from  the  country  all  winter? 
How  do  you  explain,  also,  that  there  are  in  Beauce 
cursed  fields,  in  Auvergne  dangerous  mountains,  where 
animals  from  the  farm  can  neither  be  pastured  nor 
driven,  without  paying  a  tribute,  more  or  less  great, 
to  the  disease?  From  this  is  it  not  evident  that  the 
disease  is  attached  to  the  soil,  to  the  vegetation,  and  to 
certain  climatic  conditions,  which  have  nothing  to  do 
with  this  bacteridium  in  the  blood  of  diseased  animals? 
"All  that  we  are  able  to  grant  you,"  the  skeptics 
might  have  added,  '  '  in  the  presence  of  your  proofs  and 
of  your  experiments,  is  that  this  bacteridium  is  an 
epiphenomenon.  It  sometimes  accompanies  the  virus, 
or  follows  it,  but  it  is  not  the  virus  itself.  The  virus 
of  anthrax,  like  that  of  smallpox,  or  of  sheeppox,  is 
something  which  one  can  handle  without  seeing  it  and 
recognizing  it.  It  exists,  since  the  disease  is  inoculable, 
but  we  do  not  see  it  outside  of  the  animal.  It  is  not 
something  independent  of  the  animal  but  a  modality  of 
its  being.  It  is  living,  it  may  be  granted  you,  but  it 
borrows  its  life  from  the  being  which  carries  it,  it  is 
nothing  outside  of  the  animal,  and  we  recognize  it  only 
in  transit  through  living  beings." 


DAVAINE  237 

All  these  objections  are  not  wanting  in  force,  and  as 
they  favored  idleness  of  mind  and  invited  intellectual 
repose,  they  were  very  much  in  vogue.  To  Davaine 
belongs  the  honor  of  beginning  again  the  struggle  against 
them. 


IV 
DAVAINE 


After  the  discovery  of  the  bacteridium,  which  Davaine 
had  made  in  1850,  with  Rayer,  he  had  paused  for  reflec- 
tion. His  was  a  very  keen  and  discriminating  mind. 
He  regarded  science  from  the  point  of  view  of  medicine. 
The  brief  note  by  Pasteur  in  1861  on  the  butyric  ferment, 
of  which  we  have  spoken,  had  revealed  to  him  the  exist- 
ence of  very  active  microscopic  organisms  morpholog- 
ically similar  to  the  anthrax  bacillus  and  capable,  by 
means  of  their  power  of  fermentation,  of  producing 
effects  out  of  proportion  to  their  weight  and  volume. 
Consequently,  despite  its  small  size,  the  anthrax  bacil- 
lus might  easily  cause  the  death  of  a  large  animal  and 
be  guilty  of  all  that  was  attributed  to  it.  A  singular 
thing  which  we  have  difficulty  in  explaining  to-day, 
is  the  fact  that  while  no  one  then  refused  to  admit  that 
a  thing  as  imperceptible  as  the  virus  of  smallpox  could 
convey  the  disease  and  bring  death  to  the  individual 
inoculated  with  it,  because  this  virus  seemed  to  derive 
its  energy  from  the  creature  into  which  it  penetrated, 
and  to  change  only  the  modality  of  its  life,  all  refused 
to  understand  that  the  bacillus,  an  independent  living 
organism,  could  by  its  own  activity,  triumph  over  the 
animal  which  it  invaded. 

To  Davaine  belongs  the  credit  of  having  seen  farther 
along  this  line  than  the  men  of  his  generation  and  of 


238  pasteur:  the  history  of  a  mind 

applying  himself  to  the  demonstration  of  the  fact  that 
the  bacteridium  was  the  sole  cause  of  anthrax.  Without 
entering  into  the  details  or  the  chronology  of  his  mem- 
oirs on  this  subject,  it  will  suffice  here  to  point  out  the 
status  to  which  he  had  brought  the  question  at  the  time 
when  Pasteur  attacked  it  in  so  masterly  a  manner. 

It  can  be  said  that  Davaine  had  perfectly  demon- 
strated the  coexistence  of  the  bacteridium  and  of  the 
anthrax.  This  fact  of  coexistence  which  is  not,  how- 
ever, necessarily  to  be  considered  a  relation  of  cause 
and  effect,  became  known  as  the  result  of  a  long  series 
of  observations  made  on  cases  of  malignant  pustule, 
which  is  the  most  common  form  of  anthrax  in  man,  as 
well  as  on  animals  killed  by  anthrax  either  naturally,  or 
as  a  result  of  artificial  infection.  This  coexistence  had 
been  disputed.  After  Brauell,  Signol,  Leplat  and  Jail- 
lard,  Bouley  and  Sanson  had  published  observations 
or  experiments  in  which  anthrax  seemed  to  be  present 
and  the  bacteridium  absent.  But  Davaine  had  replied 
to  this  by  showing  that  these  scientists  either  had  failed 
to  recognize  the  bacteridium  or  else  had  called  something 
anthrax  which  was  not  anthrax. 

Leplat  and  Jaillard,  for  example,  imparted  a  deadly 
malady  to  rabbits  by  inoculating  them  with  putrid 
blood  from  an  anthrax  victim,  or  in  default  of  that,  with 
bacteria  of  putrefaction,  and  did  not  find  bacteridia 
in  the  blood  of  the  dead  animals.  "  Nothing  is  less 
astonishing,"  replied  Davaine,  "your  malady,  and  also 
that  of  Signol,  is  not  anthrax.  It  differs  from  the  latter 
in  its  shorter  incubation  period,  because  it  is  accom- 
panied neither  by  the  agglutination  of  the  blood-cor- 
puscles nor  the  congestion  of  the  spleen,  the  most  con- 
stant and  characteristic  symptoms  of  anthrax,  and 
because  it  kills  birds,  on  which  the  bacteridium  has  no 
effect.     Do  not  be  surprised,  therefore,  that  in  this  new 


DAVAINE  239 

malady  there  are  no  bacteridia  in  the  blood."  The 
argument  was  solid,  well  supported  by  facts  and  en- 
tirely worthy  of  the  one  who  produced  it. 

"This  is  not  all,"  continued  Davaine,  "the  bacterid- 
ium  is  not  simply  the  inseparable  companion  of  the 
disease.  It  is  the  cause  of  it,  and  the  only  cause.  The 
proof  is  this:  As  long  as  the  bacteridium  is  not  present 
in  the  blood,  the  latter  is  not  infectious,  and  it  becomes 
so  when  the  organism  enters  it.  If  from  the  sick  animal, 
some  hours  before  its  death,  you  take  blood  with  which 
you  inoculate  another  animal  you  will  not  impart  to 
the  latter  the  disease.  If  you  inoculate  it  with  blood 
as  soon  as  the  microscope  shows  bacteridia  in  it,  the 
inoculated  animal  will  die.  If  you  wait  to  make  the 
inoculation  until  the  bacteridia  have  disappeared  under 
the  influence  of  putrefaction,  you  would  then  possibly 
obtain  the  malady  of  Leplat  and  Jaillard  but  not  anthrax. 

"You  may  say,  it  is  true,  that  in  this  experiment, 
the  blood  before,  during,  and  after  the  appearance  of 
the  bacteridium  is  not  the  same  blood,  or  at  least  may 
differ  in  other  ways  than  that  which  the  microscope 
reveals  in  the  presence  or  absence  of  bacteridia.  But 
here  is  another  argument.  Take  a  pregnant  animal, 
give  it  anthrax  and  when  it  is  dead  make  inoculations 
with  the  blood;  it  is  infectious;  at  the  same  time  make 
inoculations  with  the  blood  of  the  foetus;  it  is  not 
infectious.  This  blood  is,  nevertheless,  the  direct 
emanation  from  the  blood  of  the  mother  from  which  it 
receives  through  the  placenta  all  the  soluble  elements. 
The  placenta,  acting  as  a  filter,  keeps  out  only  the  bac- 
teridia and  because  of  their  absence  the  blood  of  the 
foetus  is  incapable  of  transmitting  anthrax. 

"Does  not  that  seem  to  you  proof?  Here  is  another 
experiment  :  Filter  blood  from  an  anthrax  victim  through 
a  porous  earthen  filter,  as  Klebs  and  Tiegel  have  done. 


240  pasteur:  the  history  of  a  mind 

No  solids  pass  through  the  filter.  The  serum  passes 
through  and  it  is  not  infectious.  The  cause  of  the  mal- 
ady is,  therefore,  not  soluble  in  the  serum.  It  remains 
on  the  surface  of  the  filter  where  there  are  only  red 
corpuscles,  white  corpuscles  and  bacteridia.  Choose 
the  cause  among  these  three,  but  choose!" 

Davaine  was  not  only  ambitious  to  demonstrate  that 
the  bacteridium  was  the  cause  and  the  only  cause  of 
the  development  of  anthrax:  he  wished  also  to  explain 
by  its  aid  the  etiology  of  the  disease,  that  is  to  say,  the 
different  conditions  governing  its  natural  appearance 
and  its  endemic  or  epidemic  character.  In  this  direc- 
tion he  was  less  successful.  He  had  observed,  as  we 
have  just  said,  that  putrefaction  rendered  the  blood 
incapable  of  transmitting  anthrax.  He  was  obliged, 
therefore,  to  give  up  seeing  in  the  blood  and  tissues  of 
an  animal  buried  as  a  victim  of  anthrax  the  cause  of  the 
revival  of  the  disease  from  one  year  to  another,  in  the 
same  region  or  pasture.  He  observed,  nevertheless,  that 
blood  rapidly  dried  preserved  its  virulence  for  a 
long  time.  Now,  said  he,  this  rapid  desiccation  must 
often  occur  in  countries  where  anthrax  is  prevalent; 
when  animals  are  slaughtered  for  the  sake  of  the  skins, 
pools  or  drops  of  blood  remain  on  the  ground,  on  the  litter, 
on  the  walls,  and  these  dry  rapidly  and  preserve  their  germs. 
As  for  the  infection  of  other  animals,  Davaine  attributed 
it  to  flies  some  of  which  by  sucking,  and  others  simply 
by  means  of  their  feet,  are  the  agents  of  infection  among 
animals  in  stables  or  the  open  field,  and  he  supported 
all  these  opinions  by  well  carried  out  experiments. 

There  were  grave  objections  to  this  etiology.  If 
it  is  the  fly  which  disseminates  the  virus,  it  was  said, 
why  does  it  sometimes  respect  so  carefully  the  bound- 
aries of  a  field  or  an  estate?  There  are  in  Beauce  and 
in  Auvergne  dangerous  fields  or  meadows;  the^adjoining 


KOCH:   THE    SPORE    OF   ANTHRAX  241 

meadows  are  not  so;  why  do  not  the  flies  pass  from  one 
to  the  other?  And  furthermore,  if  they  are  the  agents 
of  transmission  all  the  cases  of  anthrax  in  animals  ought 
to  begin  with  a  subcutaneous  tumor  or  a  lesion  of  the 
mucous  membrane,  similar  to  the  malignant  pustule  in 
man,  the  origin  of  !which  is  always  external. 

But  these  cases  of  external  anthrax  are  very  rare 
among  the  domestic  animals.  It  was  necessary,  there- 
fore, to  search  for  some  other  explanation.  But  what? 
No  one  knew.  In  the  meantime,  as  long  as  the  bac- 
teridium  did  not  explain  or  explained  so  badly  the  eti- 
ology of  the  disease,  the  partisans  of  the  theory  of  spon- 
taneous anthrax  had  a  good  chance,  and  the  opinion 
of  the  investigators  was  still  wavering  when  the  work 
of  Koch  appeared.  This  dissipated  many  of  the  obscur- 
ities and  silenced  -some  of  the  objections. 


KOCH:  THE  SPORE  OF  ANTHRAX 

It  was  in  reality  this  work  which  introduced  into  the 
question  a  very  important  idea,  that  of  the  spore,  which 
plays  so  great  a  rôle  in  our  ideas  of  to-day,  but  which 
at  that  time,  was  unknown  or  at  least  abandoned. 
Pasteur  had  observed,  in  1863,  the  formation  of  spores 
in  the  butyric  vibrios.  But  he  had  not  foreseen  their 
rôle  nor  did  he  know  their  exact  significance.  In  1869 
he  had  found  them  in  the  vibrios  of  the  fiacherie  of  the 
silkworm  and,  this  time,  he  had  proved  that  these  spores, 
these  cysts,  as  he  called  them,  had  a  resistance  greater 
than  that  of  the  rods,  and  could  endure  a  long  drying. 
By  means  of  these  cysts  he  had  explained  the  persist- 
ence of  the  epidemics  of  fiacherie  in  different  regions. 


242  pasteur:  the  history  of  a  mind 

After  Pasteur,  Cohn  had  studied  the  mode  of  formation 
and  the  resistance  of  these  spores  in  Bacillus  subtilis,  and 
had  put  forth  the  hypothesis  that  the  bacteria  of  an- 
thrax possibly  behaved  like  this  bacillus.  But  none 
of  these  precedents  detract  in  the  least  from  the  merit 
of  Koch:  it  was  he  who  showed  the  rôle  of  the  spore  in 
the  etiology  of  anthrax,  and  he  did  it  in  a  way  truly  mar- 
vellous for  its  simplicity. 

If  one  places  in  the  thermostat  or  even  leaves  exposed 
to  summer  heat  a  drop  of  fresh  beef-blood  serum  or  of 
the  aqueous  humor  of  the  eye,  sown  with  a  very  small 
fragment  of  fresh  spleen  from  a  mouse  affected  with 
anthrax,  a  microscopical  examination  at  the  end  of 
15  to  18  hours  shows  the  following  appearances:  in  the 
center  of  the  slide  which  covers  the  preparation,  where 
the  air  cannot  penetrate  easily,  the  bacilli  are  in  their 
original  state  and  have  not  elongated.  Half  way,  from 
the  edges  of  the  cover-glass  the  bacilli  are  longer,  twisted 
and  bent  and  so  much  the  more  elongated  as  they  are 
nearer  the  margin.  Certain  ones,  those  which  are  most 
in  contact  with  the  outer  air,  contain  typical  spores, 
sometimes  arranged  regularly  in  the  filament  like  beads 
(Fig.  20,  left  side).  Ultimately  these  free  themselves 
from  the  envelope  in  which  they  are  formed.  They 
are  then  disseminated  through  the  liquid  like  an  amor- 
phous powder.  But  this  dust  is  living,  for,  if  transferred 
to  a  new  drop  of  serum,  there  spores  produce  at  the  end 
of  3  or  4  hours  new  bacilli,  capable,  like  the  first,  of 
causing  the  death  of  the  animal  inoculated  with  them. 
There  is  then  no  diminution  of  virulence  in  passing 
through  the  spore  state. 

We  see  that  Koch,  passing  over  and  beyond  Davaine, 
who  had  not  thought  of  it,  was  not  satisfied  to  repeat 
Delafond's  cultural  experiments.  He  succeeded  in  the 
first  attempt  in  doing  that  which  Delafond  had  tried 


koch:  the  spore  of  anthrax  243 

to  do  in  vain — in  forcing  the  rods  of  the  anthrax  to 
produce  spores.  Furthermore  he  gave  to  this  spore  an 
important  place,  which  it  has  not  since  lost,  in  the  eti- 
ology of  the  disease.  He  did  this  by  showing  that  it 
always  forms  in  the  blood  and  tissues  of  an  animal  dead 
of  anthrax,  if  the  temperature  is  suitable  and  there  is 
sufficient  oxygen. 

These  two  conditions  are  necessary.  Below  18°C. 
spores  are  not  formed;  at  30° C.  they  occur  at  the  end  of 
30  hours;  at  35° C,  in  20  hours.  The  rapidity  with  which 
spores  are  formed  is,  therefore,  directly  proportional  to 
the  amount  of  heat.  Oxygen  is  also  indispensable. 
Anthrax  blood,  if  deprived  of  this  gas,  ceased  to  be  vir- 
ulent in  24  hours  without  putrefaction.  When  the 
blood  is  allowed  to  putrefy,  the  virulence  also  disap- 
pears if  putrefaction  exhausts  the  oxygen  quickly 
enough  so  that  the  spores  have  not  time  to  form  at  the 
temperature  to  which  they  are  exposed.  If  the  spores 
have  already  formed,  putrefaction  does  not  kill  them 
or  prevent  them  from  developing  ultimately  on  the  same 
field  or  in  the  same  region  if  circumstances  are  favor- 
able. All  the  contradictory  results  of  previous  investi- 
gators on  the  duration  of  the  virulence  of  the  blood 
or  of  diseased  organs,  some  saying  that  it  could  persist 
others  that  it  was  lost  immediately,  were  at  once 
explained.  The  persistence  of  the  disease  and  its 
return  in  an  infected  country  was  also  explained, 
and  in  an  entirely  natural  way.  It  was  the  spore  which 
was  the  agent  of  preservation,  which  persisted  where 
the  conditions  of  temperature  and  of  aeration  had  per- 
mitted it  to  form,  and  where  it  always  held  itself  in 
readiness  to  make  new  victims. 

Koch  was  not  satisfied  in  thus  broadly  explaining 
the  etiology  of  the  disease.  He  studied  the  mode  of 
transmission,    proved    that    the    symptoms  of  natural 


244  pasteur:  the  history  of  a  mind 

infection  revealed  infection  through  the  food,  and 
actually  demonstrated  that  the  small  animals  of  the 
laboratory  could  contract  anthrax  when  the  anthrax 
bacilli  or  the  spores  were  mixed  with  their  food.  For 
want  of  resources  he  could  not  make  the  same  experi- 
ments on  the  large  domestic  animals,  and  regarding 
them  he  left  the  question  an  open  one.  He  also  left 
undecided  the  problem  of  infection  by  respiration  and 
through  the  lungs.  But  science  had  nevertheless  made 
a  great  stride  when,  with  the  discovery  of  the  spore 
and  its  power  of  resistance,  there  disappeared  one  of  the 
great  objections  which  the  etiological  conception  of 
Davaine  had  raised. 

Nevertheless,  the  victory  still  remained  indecisive, 
for  a  new  adversary  had  arisen.  To  the  affirmation 
of  Koch,  P.  Bert  had  replied  in  1887  by  an  experiment 
in  which  by  exposing  anthrax  blood  to  the  action  of 
compressed  oxygen,  he  killed  or  at  least  believed  he 
killed  the  bacteridia.  Inoculation  of  this  blood  thus 
robbed  of  the  parasite  produced  the  disease  and  death, 
without  the  reappearance  of  the  bacteridia.  Therefore, 
he  concluded,  the  bacteridia  are  neither  the  cause  nor 
the  necessary  effect  of  the  anthrax  disease.  It  was 
reverting,  with  new  arguments,  to  the  idea  of  Brauell 
which  we  discussed  in  the  beginning  of  this  short  history. 


VI 
OBJECTIONS  TO  THE  NEW  DOCTRINE 

From  what  standpoint  could  a  man,  as  unfamiliar 
with  this  class  of  studies  as  Pasteur,  regard  the  facts 
which  precede,  studying  them  with  his  characteristic 
vigor?     From  what  standpoint  also  ought  the  medical 


OBJECTIONS   TO   THE   NEW  DOCTRINE  245 

men  of  the  time  to  have  regarded  these  new  ideas,  ob- 
liged as  they  were  to  reconcile  their  desire  for  the  prog- 
ress of  science  with  scholastic  traditions  and  the  hatred 
of  innovation,  so  native  to  the  practitioner.  Objec- 
tions occurred  naturally.  These  remained  vague  to 
medical  men  because  for  the  most  part  they  did  not 
have  the  laboratory  spirit,  but  they  were  formulated 
more  clearly  in  the  mind  of  Pasteur,  and  behold  the 

result  ! 

In  the  first  place  anthrax  appeared  clearly  to  be  a 
contagious,  inoculable  disease  due  to  something  which 
taken  in  an  infinitesimal  quantity  from  a  diseased 
animal  could  produce  the  disease  or  kill  a  sound  animal 
after  a  period  of  incubation  which  was  evidently  a  period 
of  development  and  of  invasion  of  the  organism.  But 
what  was  this  something?  Was  it  the  anthrax  bac- 
teridium,  as  Delafond,  Davaine  and  Koch  said?  Was 
it  a  virus,  as  tradition  would  have  it — the  tradition 
created  by  what  was  known  of  smallpox,  vaccine,  and 
sheeppox,  and  even  by  what  was  supposed  to  be  known 
about  glanders? 

The  question  does  not  seem  very  important  to  us, 
who  have  made  a  choice,  and  who,  furthermore,  with 
our  knowledge,  and  without  being  misunderstood,  are 
able  to  give  the  name  of  virus  to  the  anthrax  bacteridium 
itself.  But  20  years  ago  the  domain  of  viruses  and 
that  of  parasites  remained  separate.  M.  Chauveau,  who 
was  one  of  the  first  to  make  a  remarkable  study  along 
this  line,  defined  virulent  diseases  as  contagious  diseases 
which  were  neither  caused  nor  transmitted  by  a  parasite. 

This  distinction  not  only  seemed  well  founded,  but 
determined  the  direction  which  research  was  to  take. 
A  virus  could  be  cultivated  only  within  the  animal  or- 
ganism adapted  to  it.  It  could  enter  it  in  various  ways 
and  produce  in  it   different  manifestations  according 


246  pasteur:  the  history  of  a  mind 

to  the  point  of  entry,  but  it  did  not  on  that  account 
change  its  nature,  and  its  entity,  its  fundamental  unity 
in  the  midst  of  the  different  phases  of  the  disease  which 
it  produced,  was  the  foundation  of  the  doctrine.  With- 
out doubt  variations  in  strength,  in  virulence,  had  been 
observed  when  a  virus  was  transmitted  from  one  spe- 
cies to  another,  but  this  had  been  observed  also  and  even 
to  a  greater  degree  in  the  same  species;  epidemics  of 
smallpox  were  more  or  less  benign;  smallpox  produced 
by  inoculation  was  ordinarily  less  dangerous  than  that 
which  had  furnished  the  material  for  the  inoculation. 
All  of  these  variations  in  the  severity  of  the  disease  or 
of  the  epidemic  seemed  beyond  the  reach  of  experimen- 
tation and  were  attributed  to  external  factors,  cold, 
heat,  or  meteorological  conditions.  Such  is  the  state 
to  which  one  was  reduced  by  the  impossibility  of  ob- 
serving the  virus  outside  of  a  living  creature. 

If,  on  the  contrary,  the  bacteridium  is  a  ferment,  a 
parasite,  the  aspect  of  the  question  is  changed.  We 
can  cultivate  the  bacillus  outside  of  the  organism,  study 
its  properties,  learn  its  physiology,  and  compare  its 
physiological  with  its  pathological  rôle  to  discover  what 
effect  its  normal  functions  have  on  the  normal  functions 
of  the  animal  it  invades.  Disease  resulting  thus  from  the 
physiological  conflict  between  two  organisms  which  can 
be  studied  separately,  its  study  took  a  new  direc- 
tion. It  is  very  clear  that  Pasteur  was  not  thinking  at 
this  time  of  variations  in  virulence  among  bacteria,  nor 
of  vaccinations.  But  his  was  an  intellect  so  keen  that 
I  would  /iot  affirm  that  this  idea  was  not  in  the  back- 
ground of  his  mind  and  I  could  cite  as  an  argument  the 
eagerness  with  which  he  fell  upon  the  first  explicable  fact 
in  this  class  of  ideas.  We  shall  see  him  at  this  presently. 
In  the  first  place,  the  important  question  to  be  solved 
seemed  to  him  to  be  this  :  is  the  essential  agent  of  anthrax 


OBJECTIONS   TO   THE   NEW   DOCTRINE  247 

the  bacteridium,  or  the  virus  which  accompanies  this 
bacteridium? 

Viewed  from  this  standpoint  the  results  of  Davaine 
and  even  those  of  Koch  left  room  for  hesitation  and 
doubt.  When  one  made  inoculations,  as  Davaine  did, 
with  anthrax  blood,  he  inoculated  along  with  the  bac- 
teridia  all  the  substances  accompanying  them  in  the 
blood,  and  among  these  there  might  be  a  substance 
in  the  nature  of  a  virus,  developing  along  with  the  bac- 
teridia  in  the  inoculated  animal  and  escaping  observa- 
tion because  one  could  not  distinguish  the  virus  micro- 
scopically from  granulations  of  the  organic  liquids. 
The  bacteridium,  which  can  be  seen  and  distinguished, 
seems,  therefore,  to  develop  alone  and  to  be  the  exclusive 
cause  of  the  malady,  when  it  is  possible,  that  it  is  only 
an  epiphenomenon  as  they  say  in  the  medical  school. 

The  experiments  dealing  with  the  natural  nitration 
of  the  blood  through  the  placenta  and  of  artificial  filtra- 
tion through  a  porous  wall,  which  Davaine  presented 
as  arguments  in  favor  of  the  rôle  of  causal  agent  be- 
longing exclusively  to  the  bacteridium,  demonstrated 
only  that  this  active  rôle  was  not  vested  in  the  soluble 
elements.  We  know,  since  Chauveau's  time,  that  a 
virus  is  a  solid  organized  body  which  cannot  pass 
through  the  placenta  or  porous  plates  and  which,  re- 
maining on  the  surface  of  the  filter  with  the  bacteridium, 
may  be  inoculated  with  it. 

Koch  had  made  more  convincing  experiments  along 
this  line.  He  sowed  in  a  drop  of  serum  a  tiny  drop  of 
blood  or  bit  of  tissue  from  an  anthrax  victim,  and  left 
the  culture  to  grow.  Then,  from  this  first  culture,  he 
had  inoculated  a  new  drop  and  thus  made  8  successive 
cultures,  the  last  of  which  was  capable  of  producing  an- 
thrax in  a  healthy  animal.  But  there  again,  there  was 
room  for  a  doubt.     There  was  no  certainty  that  the 


248  pasteur:  the  history  of  a  mind 

virus  was  not  carried  by  the  blood  into  the  first  drop, 
thence  transferred  diluted  to  the  second,  third,  etc., 
and  was  still  present  in  sufficient  quantity  in  the  last  drop 
to  produce  the  effect  attributed  to  the  bacteridium. 
Chauveau's  experiments  had  just  shown  that  viruses 
could  undergo  great  dilution,  as  much  as  1/150  for  the 
vaccine,  1/500  for  glanders,  which  was  ranked  then, 
as  we  have  said,  with  smallpox  and  cowpox.  These 
cultures  of  Koch's  were  neither  numerous  enough  nor 
made  in  sufficiently  large  volumes  of  liquid  to  eliminate 
the  influence  of  the  virus  from  the  dilution.  Add  to 
that  the  results  of  P.  Bert,  which  were  still  perplexing 
to  the  partisans  of  the  new  doctrines. 

All  these  objections  appear  to  us  to-day  as  mere  hair- 
splitting. It  is  certain  that  if  any  one  should  bring 
to  us  now,  for  any  disease  whatsoever,  such  a  collection 
of  proofs  as  those  which  Davaine  and  Koch  furnished 
for  anthrax,  no  one  would  have  the  least  doubt  of  their 
significance.  Why?  Because  the  ideas  of  men  of 
research  and  of  the  public  have  orientated  in  this  direc- 
tion. The  weather-vane  has  turned;  but  this  vane 
turned  only  with  much  difficulty  and  much  squeaking. 
Davaine  and  Koch  had  blown  at  it  in  vain  with  all  the 
power  of  their  lungs,  they  had  succeeded  in  stirring  it  but 
not  in  changing  its  position.  It  was  Pasteur  who  over- 
came all  resistance  by  putting  to  rout  everything  which 
served  as  a  pretext  for  immobility  and  inaction. 

This  definite  orientation  of  mind  and  effort  was  the 
more  urgent  because  for  10  years  science  had  struggled 
with  the  difficulties  and  obscurities  of  the  subject  and 
multiplied  its  labors  and  discoveries  without  seeing 
light  burst  forth  from  any  side.  The  ideas  of  Pasteur 
on  fermentation  did  not  create  a  stir  solely  in  the 
study  of  anthrax;  the  preoccupation  with  the  rôle  of 
bacteria  in  pathology  was  general.     Klebs  had  found 


OBJECTIONS   TO   THE   NEW  DOCTRINE  249 

organisms  in  purulent  nephritis  in  1865;  Rindfleisch  in 
pyemia  in  1866;  von  Recklinghausen  and  Waldeyer 
in  metastatic  abscesses  in  1865.  In  1872  Klebs  had 
shown  how,  starting  from  a  wound,  bacteria  could  pene- 
trate the  lymphatics  or  the  veins  by  means  of  the  in- 
terstices of  the  connective  tissue,  and  from  there  infect 
the  thrombi  of  the  blood  vessels  or  produce  abscesses. 
Then  came  the  discovery  of  bacteria  in  erysipelas, 
hospital  gangrene,  puerperal  fever,  diphtheria  and  other 
diseases. 

But  on  all  these  points  there  was  still  more  legitimate 
cause  for. doubt  than  in  the  case  of  anthrax,  and  far 
from  corroborating  each  other  these  different  discov- 
eries succeeded  in  being  almost  contradictory.  Instead 
of  bringing  order,  they  seemed  to  produce  confusion.  For 
example,  contrary  to  what  appeared  logical,  pus  of  the 
same  nature  and  origin  contained  very  different  organ- 
isms and,  on  the  contrary,  forms  almost  indistinguishable 
occurred  in  very  distinct  diseases  such  as  smallpox, 
diphtheria  and  cholera.  In  a  general  way  the  organ- 
isms discovered  in  these  diseases  bore  a  striking  resem- 
blance to  each  other  and  could  scarcely  be  said  to  have 
any  special  physiognomy,  except  the  anthrax  bacter- 
idium,  on  account  of  its  size  and  because  it  was  found 
in  the  blood,  and  the  spirillum  of  recurrent  fever,  dis- 
covered in  1873  by  Obermeier,  which  also  passes  into 
the  blood  when  the  fever  is  at  its  height,  and  the  spiral 
form  of  which  serves  to  distinguish  it.  All  the  other 
organisms  were  alike  in  form,  size  and  properties,  and 
this  formed  an  argument  of  which  those  who  resisted 
the  contagion  of  the  new  ideas  were  not  slow  to  avail 
themselves. 

Finally,  to  complete  the  perplexity  of  investigators, 
bacteria  were  not  found  in  some  diseases  which  were 
clearly  of  a  contagious  nature.     After  having  set  up 


250  pasteur:  the  history  of  a  mind 

the  virus  in  opposition  to  the  microbe  these  persons  now 
asked  :  Why  are  not  bacteria  present  in  all  virulent  diseases  ? 
However,  an  answer  to  this  question  was  just  beginning 
to  be  found  in  a  simple  perfection  of  technique  which  had 
demonstrated  the  presence  of  organisms  where  their  ex- 
istence was  suspected,  but  where  they  had  not  been  seen. 
Their  discovery  was  easy  in  anthrax,  where  they  pass 
into  the  blood,  even  before  death.     It  is  more  difficult, 
even  in  anthrax,  to  trace  them  in  the  organs  of  the  body. 
There  were  only  very  imperfect  methods  for  doing  that  : 
the  treatment  of  the  tissue  with  potash,  as  Davaine 
advised,  or  with  acetic  acid,  as  in  von  Recklinghausen's 
method.     We  cannot  be  too  grateful  to  C.  Weigert  for 
the  great  service  he  rendered  in  1875  by  teaching  us 
how    to    stain    bacteria    with  basic  anilin  colors,   and 
thus  to  make  them  visible  in  the  tissues.     Two  years 
later,    Koch   achieved   a    new    advance    in    technique 
by  teaching  us   to   study  unstained   structures  micro- 
scopically with  a  very  subdued  light  and  stained  objects 
with  a  flood  of  light  [structure-picture  vs.  color-picture]. 
We  see,  from  this  brief  exposition,  that  the  science  was 
mature,  and  that,  moreover,  it  was  thoroughly  equipped 
for  new  discoveries.     What   did  it  lack?     Faith,   the 
conviction  that  it  would  not  be  deceived  on  entering 
these  new  paths,  and  that  there  were  genuine  bacterial 
diseases.     It  is  this  demonstration  that  Pasteur  gave. 


VII 

PASTEUR:  THE  BACTERIDIUM  IS  THE  SOLE  CAUSE 
OF  ANTHRAX 

To  the  question:  Is  it  a  virus?  Is  it  a  microbe?  Pas- 
teur was  happily  in  a  better  position  to  reply  than  anyv 
one  would  have  been  in  1877.     From  his  Etudes  sur 


THE  BACTERIDIUM  IS  THE  SOLE  CAUSE  OF  ANTHRAX   251 

la  bière,  and  his  contests  with  his  opponents,  he  came 
out  well  equipped,  with  a  perfected  technique,  and  a 
knowledge  both  of  bacterial  species  and  of  how  to  grow 
them.  To  solve  all  these  problems  he  could  draw  only 
from  his  own  depths,  and  this  he  showed  at  once. 

Old  observations  and  experiments  had  taught  him 
that  the  blood  of  a  sound  animal,  taken  as  it  circulates 
in  the  veins  and  exposed  to  air  which  is  free  from  germs, 
does  not  putrefy  at  the  highest  temperatures,  nor  give 
birth  to  any  organism.  It  seemed  to  him  probable, 
therefore,  for  he  knew  nothing  then  of  the  cultural  ex- 
periments of  Delafond  and  of  Koch,  that  the  blood  of 
an  animal  infected  with  anthrax,  if  sown  in  a  suitable 
medium,  would  stock  it  solely  with  anthrax  bacilli  which 
he  could  then  keep  pure  for  an  indefinite  time  in  suc- 
cessive cultures,  as  he  had  done  with  yeast  and  other 
ferments. 

Experiment  proved  it  to  be  so,  and  showed  that  this 
bacteridium  multiplies  abundantly  in  urine  made  neu- 
tral or  slightly  alkaline.  From  that  time,  the  problem 
was  solved.  Let  us  take  a  series  of  cultures  of  this 
bacteridium  transferring  each  time  one  drop  from  the 
preceding  culture  into  50  cc.  of  fresh  urine.  The  first 
dilution  is  1/1000,  the  second  1/1,000,000,  the  third 
1/1,000,000,000,  etc.  After  ten  cultures  it  falls  to 
such  a  figure  that  the  original  drop  of  blood  which 
furnished  the  first  sowing,  has  been,  so  to  speak,  drowned 
in  an  ocean.  Everything  that  it  carried  with  it,  to 
which  we  might  be  tempted  to  attribute  a  rôle  in  the 
production  of  anthrax — red  corpuscles,  white  corpuscles, 
granules  of  all  sorts— are  either  destroyed  by  the  change  of 
medium  or  are  widely  disseminated  in  this  ocean  and  are 
lost  there.  Only  the  bacteridium  has  escaped  the  dilution 
because  it  has  multiplied  in  each  of  the  cultures. 
But  a  drop  from  the  last  culture  kills  a  rabbit  or  guinea 


252  pasteur:  the  history  of  a  mind 

pig  as  surely  as  a  drop  of  anthrax  blood.  It  is,  there- 
fore, to  the  bacteridium  that  the  virulence  belongs. 
Behold  a  conclusion  of  the  first  rank  firmly  established, 
avoiding  the  objection  which  could  be  made  to  the 
corresponding  conclusion  of  Koch,  because  Pasteur, 
at  this  time,  knew  how  to  make  with  certainty  an  in- 
definite series  of  cultures,  while  Koch  learned  to  do 
this  only  later.     Such  is  the  advantage  of  technique. 

This  first  step  taken,  we  can  ask  ourselves  how  the 
bacteridium  acts.  Does  it  secrete  a  soluble  poison 
which  spreads  about  it  in  the  liquid,  as  it  undoubtedly 
spreads  in  the  tissues  of  an  attacked  animal  to  produce 
the  disease  and  kill  it?  No,  for  the  liquid  of  the  culture, 
filtered  through  a  porous  membrane  and  injected  in 
any  desired  quantity  into  a  rabbit,  barely  makes  it  sick. 
This  time  it  was  Davaine's  experiment  but  carried  on 
under  convincing  conditions  because  the  experiment  was 
not  with  a  complex  liquid  like  the  blood,  but  with  an 
artificial  culture  of  the  bacteridia. 

Finally  there  remains  the  hypothesis  that  the  bac- 
teridium itself  produces  a  virus  in  the  form  of  living 
granules  which  it  disseminates  in  the  liquid  or  in  the 
tissues,  and  which  alone  is  the  active  agent.  This 
hypothesis  accepts  the  bacteridium:  its  only  object  is 
to  connect  the  bacteria  with  the  virus,  whereas  the  actual 
current  of  events  is,  on  the  contrary,  to  connect  the 
virus  with  the  bacteria.  But  it  matters  not!  To  this 
objection,  Pasteur  and  Joubert  responded  that  nothing 
suggestive  of  virulent  granules  can  be  seen  in  the  liquid 
of  a  bacterial  culture  even  when  examined  with  the 
highest  magnifications.  There  are  only  well-defined 
filaments,  floating  in  the  midst  of  a  perfectly  clear  liquid. 
We  have  the  right  to  consider  this  reply  as  insufficient, 
since  nothing  is  to  be  seen  in  the  yellow  serosity  of  some 
pustules  of  sheeppox,  yet  we  know  that  it  is  virulent. 


CONFLICT  OF  THE  MICROBE  WITH  THE  ORGANISM      253 

Strictly  speaking,  it  is  entirely  possible  that  a  virus 
should  exist  in  the  sense  formerly  attributed  to  this 
word,  produced  by  the  bacteridium  and  accompanying 
it  in  all  its  cultures.  But  this  is  the  essential  thing, 
that  it  is  not  produced  independently  of  the  organism, 
and  that,  consequently,  whatever  the  mechanism  of 
its  action,  the  bacteridium  is  the  sole  cause  of  anthrax. 
This  is  the  demonstration  which  the  note  of  April 
30,  1877, *  gave  with  a  clearness  and  conciseness  truly 
marvelous.  It  was  said  at  the  time  and  has  been 
repeated  since,  that  it  was  unnecessary,  and  that  the 
proof  which  it  set  forth  had  already  been  made  and 
accepted  by  many  scientific  men.  Yes,  but  it  was  not 
accepted  by  all,  and  those  who  did  accept  it  were  in- 
capable of  convincing  others.  Some  of  us  had  faith, 
nobody  had  assurance  or  certainty.  Henceforth,  there 
was  a  sure  beginning  of  things,  and  a  method  of  work: 
one  could  go  ahead,  and  Pasteur  made  haste  to  reach 
the  goal  before  the  others. 


VIII 
CONFLICT  OF  THE  MICROBE  WITH  THE  ORGANISM 

In  order  to  comprehend  thoroughly  the  history  of 
his  efforts  from  this  time  on  and  not  to  be  too  much 
impressed  with  their  seemingly  disconnected  character, 
we  must  recall  the  fact  that  Pasteur  was  neither  a 
physician  nor  a  veterinary  surgeon,  and  that  the  history 
of  any  disease,  as  a  disease,  did  not  interest  him  deeply. 
That  which  he  studied  in  the  anthrax  bacteridium  was 
not  the  anthrax,  but  the  mode  of  reaction  of  the  microbe 

1  Pasteur  et  Joubert,  Charbon  et  septicémie,  Comptes  rendus  de 
l'Académie  des  Sciences,  1877. 


254  pasteur:  the  history  of  a  mind 

toward  the  organism  in  which  it  developed.  Every 
bacterial  cell  able  to  become  pathogenic  in  any  way  or 
by  any  means  whatsoever,  and  thus  to  throw  light  on 
the  mechanism  of  the  struggle  with  the  cells  of  the  host 
organism,  was  welcome  in  his  laboratory. 

It  was  for  this  reason  that  he  sometimes  passed  so  easily 
and  so  rapidly  from  one  organism  to  another.  It  was  also 
the  reason  why  he  was  so  indifferent  to  their  morphology. 
A  clever  and  positive  micrographer  who  came  to  him 
one  day  and  told  him  in  very  cautious  language  that 
a  certain  microbe  which  he  had  taken  for  a  coccus  was 
in  reality  a  very  small  bacillus,  was  very  much  aston- 
ished to  hear  him  reply:  "If  you  only  knew  how  little 
difference  that  makes  to  me."  Perhaps  he  carried  this 
disregard  of  anatomical  detail  a  little  too  far.  But 
his  rule  was  to  attack  at  once  the  most  important  things 
and  to  neglect  trifles. 

With  his  prodigious  insight,  he  had  divined  at  once 
that,  for  the  solving  of  these  problems,  he  had  a  weapon 
which  none  of  his  predecessors  had  possessed.  He  was 
able,  as  we  have  said,  to  study,  in  pure  culture,  the 
physiological  properties  of  the  bacteridium,  or  of  any 
other  microbe,  and  to  compare  them  in  their  pathological 
reaction.  In  other  words,  he  could  establish  the  eti- 
ology of  the  disease,  not  only  by  establishing  more  firmly 
than  had  hitherto  been  done  a  relation  of  cause  and 
effect  between  the  microbe  and  the  disease,  but  by 
connecting  each  one  of  the  symptoms  of  the  disease 
with  the  reaction  of  the  physiology  of  the  micro-organ- 
ism on  that  of  the  tissues.  This  was  the  new  program, 
which  he  pursued  instinctively,  perhaps  without  delib- 
erate intention,  but  led  by  his  habits  of  mind  and  the 
trend  of  affairs  in  his  laboratory.  At  once,  he  reaped 
a  harvest  of  discoveries. 

For   example,    the   anthrax   bacteridium   is   aerobic, 


CONFLICT  OF  THE  MICROBE  WITH  THE  ORGANISM      255 

as  Koch  had  seen,  and  must  have  contact  with  oxygen 
in  order  to  live.  Therefore,  as  soon  as  the  bacteria 
reach  the  blood  they  struggle  with  the  red  corpuscles 
for  the  possession  of  this  gas,  and,  consequently,  the 
latter  are  asphyxiated.  Thus,  clearly,  originates  the 
black  color  of  the  blood  and  viscera  at  the  moment 
of  death,  which  is  one  of  the  most  marked  character- 
istics of  anthrax. 

These  corpuscles  of  anthrax  blood  are,  furthermore, 
agglutinated  and  massed  together.  Why?  Because 
of  a  secretion  of  the  bacteria.  Anthrax  serum  filtered 
and  mixed  with  fresh  normal  blood  agglutinates  the 
corpuscles  as  much  and  even  more  than  occurs  natu- 
rally in  the  disease,  due,  without  doubt,  to  a  diastase 
which  the  bacteria  have  secreted  in  the  culture  medium. 
Here  we  have  the  first  example  introduced  into  science 
of  a  bacterial  secretion  producing  one  of  the  symptoms 
of  a  disease. 

The  second,  still  more  striking,  was  taken  some  months 
later  from  the  history  of  chicken  cholera.  One  of  the 
most  curious  symptoms  of  this  disease  is  the  uncon- 
querable somnolency  which  overtakes  the  diseased 
fowls.  But  one  can  produce  a  somnolence  entirely 
similar  though  less  profound  by  inoculating  a  healthy 
animal  with  a  filtered  culture  of  the  microbe  of  chicken 
cholera.  The  filtered  liquid  is  free  from  the  microbe 
but  contains  substances  secreted  by  it,  which  we  call 
to-day  its  toxines,  and  this  word  alone  is  sufficient  to 
recall  all  that  has  sprung  with  time  from  this  fundamen- 
tal observation  of  Pasteur  concerning  which  we  have 
just  spoken. 

We  are  not  yet  done  with  this  note  of  the  16th  of  July, 
1877,  from  which  we  have  derived  the  preceding  facts. 
There  are  some  species  of  animals  which  are  refractory  to 
anthrax.     Such  are  the  birds.     Nevertheless  the  blood 


256  pasteur:  the  history  of  a  mind 

of  a  bird,  drawn  from  the  animal,  is  an  excellent  culture 
medium  for  the  bacteridium.  Why  does  it  resist  in- 
fection in  the  animal?  Because  "the  living  blood  in 
full  circulation  is  filled  with  an  infinite  number  of  cor- 
puscles which  in  order  to  live  and  perform  their  physio- 
logical function,  need  free  oxygen:  it  might  be  said  that 
the  blood  corpuscles  are  obligate  aerobes.  When,  there- 
fore, the  anthrax  bacteridium,  enters  normal  blood, 
it  meets  there  an  enormous  number  of  organic  indi- 
vidualities ready,  figuratively  speaking,  for  what  one 
sometimes  calls  the  struggle  for  existence,  ready,  in 
other  words,  to  seize  for  their  own  use  the  oxygen  nec- 
essary for  the  existence  of  the  bacteridium."1 

We  see  developed  here  the  formula  and  the  ideas  of 
Darwin,  but  in  a  singularly  precise  form.  What  could 
be  more  vague  than  the  phrase  "struggle  for  existence?" 
But  "struggle  for  oxygen,"  that  opens  the  way  to  ex- 
perimentation, and  Pasteur  begins  at  once. 

Some  common  bacteria  sown  with  the  anthrax  bacter- 
idium, in  neutral  or  alkaline  urine,  prevent  its  developing 
because  they  take  possession  of  the  ground  more  rapidly 
and  exhaust  the  oxygen.  They  can,  in  the  same  way, 
arrest  its  development  in  an  animal.  "It  is  possible 
to  inject  great  quantities  of  the  anthrax  bacteridium 
into  an  animal  without  its  contracting  the  disease,  if 
some  of  these  common  bacteria  have  been  present  in 
the  culture  used."  Here  we  have  the  first  example  of 
bacteriotherapy,  to  which  Cantani  returned  later,  and 
which  has  not  spoken  its  last  word. 

The  interpretation  of  these  facts  has  changed,  and 
we  know  now  that  it  is  less  simple  [than  it  seemed  at  that 
time]  but  the  idea  of  the  struggle  for  existence  was  never- 
theless then  introduced  into  pathology,  in  the  domain 
of  cellular  antagonism:  and  it  has  remained  there. 

1  Comptes  rendus  de  l'Académie  des  Sciences,  16  juillet,  1877. 


THE    SEPTIC   VIBRIO  257 

.IX 
THE  SEPTIC  VIBRIO 

This  idea  also  shed  a  light  over  the  past.  We  have 
seen  that  MM.  Leplat  and  Jaillard  had  contested  the 
interpretations  of  Davaine  by  showing  that  an  animal 
inoculated  with  putrid  anthrax  blood  died  quickly  with 
symptoms  analogous  to  those  of  anthrax,  but  without 
having  bacteridia  in  the  blood,  a  proof  to  them  that  the 
presence  of  the  bacteridium  in  anthrax  was  only  an 
epiphenomenon.  To  that,  Davaine  had  replied  that 
the  disease  produced  by  Leplat  and  Jaillard  was  not 
anthrax,  but  differed  from  it  in  the  length  of  the  incu- 
bation period  and  in  many  other  ways.  He  was  right, 
but  exacting  minds,  and  it  is  always  necessary  that  there 
should  be  such  in  science,  were  justified  in  finding  his 
reasons  insufficient.  It  might  be,  after  all,  that  the 
disease  produced  by  Leplat  and  Jaillard  was  the  true 
anthrax  and  Davaine's  was  an  anthrax  modified  by 
the  presence  of  the  bacteridium.  The  intervention  of 
this  microbe  might  well  change  the  symptoms,  modify 
the  evolution  of  the  disease,  and  permit  it  to  attack 
other  species  of  animals. 

How  was  one  to  meet  this  objection,  which  was  like 
viewing  the  same  facts  through  opposite  ends  of  the 
lorgnette?  There  would  have  been  one  way,  viz.,  to  dis- 
cover the  cause  of  Leplat  and  Jaillard's  disease.  But 
in  his  attempt  to  do  this  Davaine  was  shipwrecked,  in 
spite  of  his  efforts.  He  had  found  the  anthrax  bacillus 
in  the  blood:  it  was  in  the  blood  that  he  searched  ob- 
stinately for  the  second  disease,  but  he  found  nothing 
there.  If  it  had  occurred  to  him  to  examine  the  tissues 
he  might  have  found  myriads  of  the  organisms  which  he 
sought.     The  abdominal  serosity  in  particular  is  full 

17 


258  pasteur:  the  history  of  a  mind 

of  them,  it  is  almost  a  pure  culture  of  the  microbe  (Fig. 
21),  while  in  the  blood  the  rods  are  rare,  more  elongated 
and  difficult  to  find  in  the  midst  of  the  corpuscles;  fur- 
thermore, they  enter  the  blood  late  in  the  course  of 
the  disease  and  Davaine  had  not  seen  them  there.     Thus 


Fig.  21. — The  septic  vibrio  in  the  abdominal  serosity  and  in  the  blood. 
In  the  serosity  the  forms  are  variable.  In  the  blood  they  are  long  filaments, 
infrequent  and  hard  to  see  in  the  midst  of  the  corpuscles. 

it  is  that  one  can  just  fail  of  making  the  most  beau- 
tiful discovery. 

Pasteur,  for  whom  everything  was  a  pretext  for  micro- 
scopical study,  did  not  allow  this  opportunity  to  escape, 
and  threw  himself  with  his  customary  ardour  into  the 
study  of  this  new  microbe.  There  also,  a  harvest  of 
facts  awaited  him. 


THE    SEPTIC  VIBRIO  259 

This  one,  immediately:  This  organism  is  a  common 
one.  The  disease  which  it  causes  is  identical  with 
that  which  Signol  had  produced,  two  years  before,  by 
inoculating  with  blood  taken  from  the  deep-lying  veins 
of  a  healthy  animal,  asphyxiated  15  or  20  hours.  In 
this  case  the  bacteria  reach  the  blood  by  way  of  the 
intestinal  canal  which  often  contains  millions  of  them, 
but  where  they  are  harmless.  Only  after  death  do  they 
pass  the  barrier  which  this  canal  opposes  to  them,  and 
reach  the  organs  and  the  blood. 

It  was  the  same  bacterium  that  was  present  in  Leplat 
and  Jaillard's  putrid  anthrax  blood  :  as  the  disease  which 
it  causes  develops  more  rapidly  than  anthrax,  it  gets 
the  better  of  the  latter  in  the  animals  which  have  been 
inoculated  with  this  blood  and  we  see  it  alone.  Davaine, 
therefore,  was  right.  The  animals  which  Leplat  and 
and  Jaillard  inoculated  did  not  die  of  anthrax,  and  it 
was  left  for  Pasteur  to  tell  what  killed  them. 

Finally,  it  was  probably  this  same  organism  which 
caused  the  illusion  of  P.  Bert.  The  blood  in  which  he 
believed  that  he  had  killed  the  bacteridia  with  oxygen, 
and  which  gave  anthrax  without  microbes  when  inocu- 
lated, very  probably  contained  Signol's  organism  pro- 
tected by  its  spore  stage  against  the  action  of  oxygen, 
and  bringing  to  the  inoculated  animal  the  disease  of 
which  it  is  the  agent.1 

Thus  disappeared  with  one  wave  of  the  wand  the 
greatest  of  the  objections  to  the  new  etiology  of  anthrax. 
But  this  was  not  all.  Pasteur  made  haste  to  subject 
the  new  bacterium,  which  he  has  made  famous  under 
the  name  of  septic  vibrio,  to  that  physiological  study 

1  This  disease,  common  to  man  and  various  domestic  animals,  is  known 
variously  to-day  as  gangrenous  septicemia,  malignant  cedema,  traumatic 
gangrene,  gaseous  gangrene,  etc.  It  is  believed  to  be  due  to  various 
distinct  anaerobes  called  Vibrion  septique,  Bacillus  œdematicus,  Bacillus 
welchii,  Bacillus  egens,  etc.      Trs. 


260  pasteur:  the  history  of  a  mind 

which  had  been  so  successful  with  the  anthrax  bac- 
teridium.  He  saw  at  once  that  he  could  cultivate 
it  only  in  the  absence  of  air,  as  it  was  an  obligate 
anaerobe. 

Therefore,  he  concluded,  with  the  assurance  that  long 
practice  had  given  to  him,  it  is  a  ferment,  and,  in  fact, 
in  culture  media  it  liberates  gas,  forms  carbonic  acid, 
hydrogen  and  a  small  amount  of  hydrogen  sulphide 
which  imparts  an  odor  to  the  mixture.  How  is  it  that 
this  fact  was  not  deduced  at  once  from  that  other  fact, 
namely  that  when  a  post-mortem  is  made  on  an  animal 
which  has  died  of  septicemia,  we  find  tympanites,  gas 
pockets  in  the  cellular  tissue  of  the  groin  or  of  the  axilla, 
and  frothy  bubbles  in  the  serosity  which  flows  from  all 
points  in  the  body  when  an  opening  is  made.  The 
animal  exhales  a  characteristic  odor  toward  the  end 
of  its  life.  Its  parasites,  driven  out  it  may  be  by  this 
production  of  hydrogen  sulphide,  leave  the  skin  to  take 
refuge  at  the  extremity  of  its  hairs.  In  short,  septicemia 
may  be  termed  a  putrefaction  of  the  living  organism. 

When  the  anaerobic  character  of  the  septic  vibrio 
was  once  discovered,  a  series  of  logical  deductions  at 
once  presented  themselves. 

"When  a  liquid  containing  the  septic  vibrio  is  ex- 
posed to  pure  air,  the  bacteria  ought  to  be  killed  and 
all  virulence  destroyed.  That  is  what  happens.  When 
some  drops  of  septic  serosity  are  spread  out  in  a  very 
thin  layer  in  a  tube  placed  horizontally,  in  less  than  half 
a  day  the  liquid  becomes  absolutely  harmless,  even 
though  in  the  first  place  it  was  so  virulent  that  inocu- 
lation with  the  very  smallest  fraction  of  a  drop  would 
produce  death. 

"Furthermore,  all  the  vibrios  which  occur  in  profusion 
in  the  liquid  in  the  form  of  motile  filaments,  are  de- 
stroyed and   disappear.     We  find  after  this  exposure 


THE   SEPTIC  VIBRIO  261 

to  the  air  only  fine  amorphous  granules,  which  cannot 
be  cultivated  and  which  will  not  communicate  any 
disease  whatsoever.  One  might  say  that  the  air  burns 
up  the  vibrios. 

"If  it  is  terrifying  to  think  that  life  is  at  the  mercy 
of  the  multiplication  of  these  infinitely  small  organisms, 
it  is,  on  the  other  hand,  consoling  to  hope  that  science 
will  not  always  remain  powerless  before  such  enemies, 
since  having  barely  begun  the  study  of  them,  she  has 
taught  us,  for  example,  that  simple  contact  with  the 
air  is  sometimes  sufficient  to  destroy  them."1 

The  progress  we  have  just  made  seems  perplexing 
in  the  light  of  what  we  already  know.  How  can  sep- 
ticemia exist  if  air  destroys  the  vibrios?  How  can  the 
blood,  kept  in  contact  with  the  air,  become  or  remain 
septic?  How  did  Leplat  and  Jaillard,  who  had  no  idea 
of  anaerobic  life  and  its  demands,  obtain,  almost  at 
once,  septicemia  in  the  animals  they  inoculated?  The 
reason  for  this  is  that  all  we  have  said  is  true  for  vibrios 
in  course  of  development  but  it  does  not  hold  good  for 
the  spores.  The  latter  do  not  form  in  contact  with  air. 
They  are  not  produced  in  the  serosity  spread  out  in  a 
thin  layer  such  as  that  just  described.  But  place  the 
same  quantity  of  serosity  in  a  tube  of  small  diameter 
which  we  keep  upright,  and  allow  the  oxygen  to  act  on 
it  in  the  same  way  and  all  will  be  changed.  The  vibrios 
on  the  surface  die  by  absorbing  oxygen  and  thus  protect 
those  in  the  depths,  which  have  time  to  form  spores. 
The  latter,  once  formed,  have  nothing  to  fear  from  the 
air,  and  the  liquid  which  the  oxygen  had  rendered  harm- 
less in  the  first  instance,  here  remains  virulent,  because 
instead  of  being  in  a  horizontal  tube  it  is  in  a  vertical 
one. 

xLa   Théorie  des  germes  et  ses  applications  à  la  Médecine  et  à  la 
Chirurgie.     Lecture  faite  à  l'Acad.  de  Médecine,  le  28  avril,  1878. 


262  pasteur:  the  history  op  a  mind 

Pasteur  who  believed  he  could  never  accumulate  too 
much  proof  in  support  of  his  opinion,  was  here  not  un- 
mindful of  the  fact  that  the  animate  cause  of  certain 
virulent  diseases  was  still  contested.  He  had  a  beautiful 
argument  to  add  to  those  which  he  had  already  given 
on  anthrax.  He  made  it  instantly  in  the  same  shrewd 
way  that  he  made  an  ingenious  analysis. 

"We  should  search,"  he  says,  "for  proof  that  apart 
from  our  vibrio  there  is  no  independent  virulence  pecu- 
liar to  liquids  or  solids,  that,  in  short,  the  vibrio  is  not 
simply  an  epiphenomenon  of  the  disease  of  which  it 
is  the  obligate  associate" (I.e.).  Here  are  two  liquids 
which  are  identical  in  the  beginning,  exposed  to  air  for 
the  same  length  of  time.  One  remains  virulent,  the 
other  does  not. 

They  contained  originally  and  both  still  contain  two 
kinds  of  substances — solids  and  fluids.  To  which  does 
the  virulence  belong?  It  is  evident  that  the  substances 
in  solution  have  remained  the  same  in  both  cases.  It 
is  not  possible  to  imagine  any  action  produced  on  them 
by  the  air  which  would  not  be  alike  in  both  tubes.  Only 
the  solids,  and  there  are  none  except  the  vibrios,  have 
undergone  a  change,  being  converted  into  resistant  spores 
in  one  case,  and  harmless  granules  in  the  other.  It 
is,  therefore,  to  these  alone  that  the  virulence  must  be 
attributed. 

We  have  not  finished.  We  have  just  demonstrated 
that  the  spore  is  the  resistant  aerobic  form  of  the  anae- 
robic vibrio.  How  does  it  return  to  the  vibrio  stage? 
This  is  equivalent  to  asking,  since  the  spore-form  occurs 
everywhere,  under  what  circumstances  does  it  again 
become  dangerous?  We  shall  soon  see  with  what  bril- 
liancy Pasteur  answers  this  question. 


A    COMMON   MICROBE   MAT   BE   PATHOGENIC  263 

X 

A  COMMON  MICROBE  MAY  BE  PATHOGENIC 

The  septic  vibrio,  we  have  said,  occurs  everywhere. 
Almost  always  there  are  billions  of  them  in  the  intes- 
tinal canal  of  all  animals.  We  invariably  find  them 
in  the  soil,  and,  from  studies  on  the  etiology  of  anthrax, 
which  we  shall  meet  again  shortly,  Pasteur  was  con- 
vinced that  the  chances  were  very  great  that  a  guinea 
pig  or  a  rabbit  inoculated  with  drainage  water  from 
any  soil  whatsoever  would  die  of  septicemia. l 

Here,  therefore,  we  have  a  very  common  organism, 
which  we  discover  to  be  very  dangerous  and  capable 
of  causing  a  deadly  malady  when  it  enters  the  tissues 
through  a  wound.  Why  this  penetration  of  the  tissues 
does  not  occur  more  often  and  why  the  malady  induced 
thereby  is  not  inscribed  on  the  list  of  prevalent  diseases 
was  an  embarrassing  question,  and  one  with  which  the 
partisans  of  the  theory  of  the  spontaneous  generation 
of  disease  should  have  triumphed.  "You  see  clearly," 
they  might  have  said,  "that  something  more  than  the 
microbe  is  needed  to  make  us  ill,  since  in  this  case  we 
so  often  find  the  organism  and  so  rarely  the  disease." 
Pasteur  knew  well  that  he  laid  himself  open  to  attack, 
since  this  theory  would  not  be  easily  accepted,  that  a 
common  organism  could  become  pathogenic  under 
certain  conditions  and  at  certain  times,  and  it  was  for 
this  reason  that  at  the  end  of  his  Note  to  the  Academy 
of  Medicine  he  gathered  together  examples  and  proofs 
of  this  fact.  This  Note,  which  seems  a  little  disconnected, 
is  unified  only  when  it  is  regarded  in  this  light. 

1  Examinations  made  during  the  late  German  war,  in  which  gas  gan- 
grene very  commonly  followed  neglected  wounds,  indicate  that  this 
organism  or  one  acting  like  it  occurs  in  practically  every  gram  of  soil  in 
Northern  France  and  Belgium.     Trs. 


264  pasteur:  the  history  of  a  mind 

His  method  was  as  follows:  to  demonstrate  for  the 
septic  vibrio  that  the  return  of  the  spore  to  activity 
and  to  virulence  does  not  depend  on  the  obscure  questions 
of  vital  force  or  vital  resistance,  which  medicine  invokes 
so  readily,  but  that  it  is  simply  a  question  of  the  pres- 
ence or  absence  of  oxygen;  then,  when  he  had  thus 
smoothed  the  way,  to  marshal  together  and  launch, 
somewhat  pell-mell,  other  analogous  facts  regarding 
the  ability  of  water-  and  soil  microbes  to  become  patho- 
genic. Now  that  we  know  his  plan  of  campaign  let 
us  see  how  he  carried  it  out? 

In  the  first  place  let  us  ask  if  "the  germ  corpuscles 
of  the  septic  vibrio,  although  formed  in  a  vacuum  or 
in  pure  carbonic  acid  gas,  would  not  need,  in  order  to 
become  active,  a  small  quantity  of  oxygen.  Physiology 
does  not  know  to-day  of  any  case  in  which  germination 
is  possible  in  the  absence  of  air. 1  So  be  it  !  nevertheless, 
experiment  has  shown  that  the  germs  of  the  septic  vibrio 
are  absolutely  inactive  in  contact  with  oxygen,  whatever 
may  be  the  proportion  of  this  gas;  but  this  is  always 
on  condition  that  there  is  a  certain  relation  between  the 
volume  of  air  and  the  number  of  germs,  for  the  first 
germinations,  using  up  the  air  which  is  in  solution,  may 
serve  as  a  protection  for  the  remaining  germs,  and  it  is 
thus  that,  actually,  the  septic  vibrio  may  propagate  itself 
even  in  the  presence  of  small  quantities  of  air,  but  not 
if  much  air  is  present." 

That  is,  if,  in  addition  to  the  septic  vibrio,  there  are 
present  common  aerobic  bacteria,  the  latter  by  de- 
veloping, prepare  the  way  for  the  former.  Thus  it  is 
that  the  vibrio  develops  in  the  intestinal  canal,  which  is 
ordinarily  destitute  of  oxygen,  and  Pasteur  here  recog- 
nized once  more  the  rôle  played  by  associations  of  bac- 

1  Rice  and  some  other  seeds  are  now  known  to  germinate  in  this  way. 
See  paper  by  Takahashi.  Bull.  Imp.  Agr.  Col.,  Tokyo,  1905.  Vol.  6, 
p.  439,  Trs. 


A   COMMON   MICROBE   MAY  BE    PATHOGENIC         265 

teria  which  we  have  dwelt  upon  throughout  this  book 
and  which  he  understood  so  well. 

Preoccupied  as  he  was  with  the  application  of  these 
facts  to  medicine,  he  could  not  fail  to  write,  at  this  stage, 
the  following  lines,  the  advantage  of  which  we  shall 
find  once  more  at  the  end  of  this  chapter. 

"A  curious  therapeutic  observation  presents  itself. 
Let  us  suppose  a  wound  exposed  to  the  air  and  under 
putrefying  conditions  leading  to  the  accident  of  simple 
septicemia  in  the  patient,  I  mean  without  other  compli- 
cations than  would  result  from  the  development  of  the 
septic  vibrio.  Theoretically,  at  least,  the  best  means  of 
preventing  death  would  be  to  wash  the  wound  unceas- 
ingly with  common  aerated  water,  or  to  flood  the  sur- 
face with  atmospheric  air.  The  adult  septic  vibrios, 
about  to  divide  by  fission,  would  die  in  contact  with 
the  air;  as  to  their  germs,  they  would  not  grow. 
Furthermore,  one  might  expose  the  surface  of  the  wound 
to  air  heavily  charged  with  the  germs  of  the  septic 
vibrio,  or  wash  it  with  water  holding  in  suspension  billions 
of  these  germs  without  producing  the  least  septicemia 
in  the  patient.  But  under  similar  conditions  let  a  single 
clot  of  blood,  or  a  single  fragment  of  dead  flesh,  lodge 
in  a  corner  of  the  wound  sheltered  from  the  oxygen  of 
the  air,  where  it  remains  surrounded  by  carbonic  acid 
gas,  even  though  it  might  be  over  a  very  small  area, 
and  beginning  at  once  the  septic  germs  will  give  rise, 
in  less  than  24  hours,  to  an  infinite  number  of  vibrios 
multiplying  by  fission  and  capable  of  causing  in  a  very 
short  time  a  mortal  septicemia." 

And  immediately,  through  the  door  he  has  opened, 
he  passes  a  whole  series  of  similar  cases.  There  is, 
for  example,  in  common  waters  from  the  most  varied 
sources,  another  vibrio  both  aerobic  like  the  bacter- 
idium  of  anthrax  and  anaerobic  like  the  septic  vibrio, 


266  pasteur:  the  history  op  a  mind 

inoculation  of  which  into  a  guinea  pig  produces  pus 
collections  or  abscesses,  that  is  to  say,  a  pathological 
condition  very  different  from  that  produced  by  either 
the  anthrax  bacillus  or  the  septic  vibrio.  Its  power  of 
producing  pus  is  so  great  that  it  still  does  so  even  though 
the  inoculation  is  made  after  the  vibrio  has  been  killed 
by  the  action  of  heat  and  thus  it  behaves  like  an  inert 
body.  This  should  interest  you,  you  medical  men, 
we  seem  to  hear  Pasteur  saying,  for,  with  this  organism 
one  can  obtain  those  celebrated  metastatic  abscesses 
which  have  puzzled  you  so  much  from  the  time  of 
Hippocrates.  When  it  is  inoculated,  living  or  dead, 
into  the  veins  so  that  the  circulation  will  distribute 
it  throughout  the  tissues,  we  see  the  lungs,  the  liver 
and  other  organs  filled  within  24  hours  with  an  infinite 
number  of  metastatic  abscesses  in  all  stages  of  develop- 
ment. Why  should  it  be  astonishing  that  a  diseased 
organ  can  do  the  same  thing  in  a  living  being,  if  it 
empties  its  parasites  into  a  blood  vessel? 

Here  again,  as  is  always  the  case  in  ordinary  water 
and  in  the  air,  there  are  other  anaerobic  vibrios  which, 
when  introduced  into  the  tissues,  do  not  develop  there 
for  various  reasons:  in  one  case,  because  the  normal 
temperature  of  the  body  is  too  high;  in  another  case, 
because  the  healthy  tissues  are  too  well  supplied  with 
oxygen.  But  diminish  in  any  way  whatsoever  this 
vital  resistance,  which,  mark  my  words,  has  no  abstract 
significance  in  my  discourse,  and  always  represents  a 
concrete  force,  and  you  will  see  these  microbes  hitherto 
dormant,  take  possession  of  the  organism  and  combine 
their  actions  and  efforts  to  produce  purulent  septi- 
cemias or  purulent  septic  infections.  These  are  the 
enemies  with  which  we  are  threatened  on  all  sides  in 
ordinary  life,  and  to  which  we  are  still  further  exposed 
when  the  surgeon  intervenes  and  causes  or  repairs  lesions 


A   COMMON   MICROBE    MAY  BE   PATHOGENIC  267 

in  the  tissues.  "This  water,  this  sponge,  this  lint  with 
which  you  wash  or  cover  a  wound,  deposit  germs  there 
which,  as  you  see,  have  an  extreme  facility  for  multiplying 
within  the  tissues  and  which  would  infallibly  cause  the 
death  of  the  patient  in  a  very  short  time,  if  the  body 
by  its  vital  processes  did  not  check  the  multiplication 
of  these  germs.  But  alas,  how  many  times  this  vital 
resistance  is  impotent,  how  often  the  constitution  of 
the  wounded  man,  his  weakness,  his  morale,  and  bad 
dressing  of  the  wound  oppose  only  an  insufficient  barrier 
to  the  invasion  of  these  infinitely  small  organisms  with 
which,  unwittingly,  you  have  entirely  covered  him  in  the 
injured  part.  If  I  had  the  honor  to  be  a  surgeon, 
impressed  as  I  am  with  the  dangers  to  which  the  patient 
is  exposed  by  the  germs  of  microbes  scattered  over  the 
surface  of  all  objects,  particularly  in  hospitals,  not  only 
would  I  use  none  but  perfectly  clean  instruments,  but 
after  having  cleansed  my  hands  with  the  greatest  care 
and  subjected  them  to  a  rapid  naming,  which  would  ex- 
pose them  to  no  more  inconvenience  than  that  felt  by  a 
smoker  who  passes  a  glowing  coal  from  one  hand  to 
the  other,  I  would  use  only  lint,  bandages  and  sponges 
previously  exposed  to  air  of  a  temperature  of  130°  to 
150°C;  I  would  never  use  any  water  which  had  not  been 
subjected  to  a  temperature  of  110°  to  120°C.  All  this 
is  very  practical.  In  this  way,  I  would  only  have  to  fear 
the  germs  in  suspension  in  the  air  around  the  bed  of  the 
patient;  but  observation  shows  us  daily  that  the  num- 
ber of  these  germs  is,  so  to  speak,  insignificant  in  com- 
parison with  those  distributed  in  the  dust  on  the  surface 
of  objects,  or  in  the  clearest  ordinary  water.  And,  fur- 
thermore, nothing  should  prevent  the  use  of  antiseptic 
methods  in  dressing  wounds,  but,  joined  with  the  pre- 
cautions I  have  indicated,  these  methods  of  procedure 
could  be  very  greatly  simplified.     A  weak  phenic  acid, 


268  pasteur:  the  history  of  a  mind 

which  consequently  does  not  affect  the  hands  of  the 
operator,  or  cause  him  trouble  in  breathing,  could  be 
advantageously  substituted  for  a  caustic  phenic  acid." 

It  was  in  this  way,  scarcely  raising  the  tone  of  his 
voice,  and  without  any  high  sounding  phrases  but 
merely  by  following  rigorously  and  patiently  the  thread 
of  his  thought  that  Pasteur  compelled  surgeons  to  per- 
fect the  methods  for  dressing  wounds  which  had  been 
employed  by  Lister,  and  which  had  themselves  been 
such  a  great  discovery.  These  methods  had  been  in- 
spired by  an  inexact  idea  as  to  the  true  state  of  affairs, 
an  idea  which  Pasteur  had  shared,  as  we  have  seen,  but 
from  which  he  detached  himself,  more  and  more. 
This  idea  was  that  the  air,  especially,  was  to  be  feared 
as  the  conveyor  of  germs.  In  this  memorable  note, 
we  have  Pasteur  laying  the  blame  upon  the  sponges, 
the  lint,  and,  without  wishing  to  put  it  into  so  many 
words,  upon  the  surgeon  himself. 

To  make  this  idea  acceptable  to  the  illustrious  prac- 
titioners, his  colleagues  in  the  Academy  of  Medicine, 
that  they  were  responsible  for  the  accidents  which  oc- 
curred to  their  patients,  and  that  when  there  was  a 
case  of  death  by  purulent  infection  in  their  service,  or 
even  merely  a  case  of  operative  fever  it  was  their  fault, 
was  a  task  that  Pasteur  had  not  ventured  to  assume, 
and  yet  one  which  he  accomplished;  because  the  new  was 
certain  to  destroy  the  old,  because  it  was  only  necessary 
to  leave  to  itself  the  idea  lodged  in  this  Note  in  order 
to  see  it  invade  and  overthrow  everything.  Modern 
surgery  has  arisen  full  fledged  from  this  Note  of  1878, 
the  general  outlines  of  which  we  have  just  traced. 

"Some  weeks  ago,"  said  Pasteur  in  conclusion,  "one 
of  the  members  of  the  Section  of  Medicine  and  Surgery 
of  the  Academy  of  Sciences,  M.  Sédillot,  after  long 
meditation  on  the  things  he  had  learned  in  the  course 


NEW   EXAMPLES   OF   PHYSIOLOGICAL   CONFLICTS     269 

of  a  brilliant  career,  did  not  hesitate  to  declare  that 
success  and  failure  in  surgery  found  a  rational  explana- 
tion in  the  principles  on  which  rests  the  so-called  theory 
of  germs,  and  that  this  would  give  rise  to  a  new  surgery, 
that  already  inaugurated  by  a  celebrated  English  surgeon, 
Dr.  Lister,  who  was  one  of  the  first  to  understand  its 
fecundity.  Without  any  professional  competence,  but 
with  the  conviction  of  a  qualified  experimenter,  I  ven- 
ture to  repeat  here  the  words  of  our  eminent  confrère." 


XI 

NEW  EXAMPLES   OF  PHYSIOLOGICAL  CONFLICTS 

In  this  rapid  review  of  the  etiological  work  of  Pasteur 
I  have  naturally  omitted  some  details  which  seem  to 
me  secondary,  and  some  ideas  which  would  have  con- 
stituted merely  replicas  of  ideas  already  well-known. 
Pasteur  studied,  or  caused  to  be  studied  under  his  eyes, 
all  the  bacteria  which  he  could  find,  however,  little  patho- 
genic they  were  or  appeared  to  be.  As  I  have  said, 
that  which  interested  him  was  the  pathological  conflict 
between  the  physiological  properties  of  the  micro- 
organism and  of  the  cells  of  the  tissues,  and  for  examples 
of  this  conflict  he  searched  everywhere. 

As  the  laboratory  was  not  a  hospital  we  scarcely  saw 
diseases  there;  he  was  obliged  to  profit  by  the  indisposi- 
tions of  the  personnel.  I  was,  just  at  this  moment, 
beset  by  a  series  of  boils  and  the  first  thing  that  Pasteur 
did  when  I  showed  him  one  of  them  was  to  prick  it, 
or  rather  have  it  pricked,  for  he  was  not  fond  of  operating 
himself,  and  to  take  therefrom  a  drop  of  blood  in  order 
to  make  a  culture,  in  which  undertaking  he  was  success- 
ful. A  second  boil  gave  the  same  result,  and  thus  the 
staphylococcus  was  discovered  which  since  that  time 


270  pasteur:  the  history  of  a  mind 

has  been  so  well  known.  He  found  the  same  microbe, 
made  up  of  little  agglomerated  granules,  in  the  pus  of 
an  infectious  osteomyelitis  which  M.  Lannelongue  had 
submitted  to  him  for  examination,  and  we  see  him, 
declaring  immediately  with  a  fine  audacity  that  the 
osteomyelitis  and  the  boil  are  two  forms  of  one  and  the 
the  same  disease,  and  that  the  osteomyelitis,  which  is 
a  suppuration  of  the  marrow,  is  the  boil  of  the  bone. 
What  could  be  worse  than  to  liken  a  grave  malady 
taking  place  in  the  depths  of  the  tissues  to  a  superficial 
malady,  which  is  generally  trifling!  To  confound 
internal  and  external  pathology!  When  he  launched 
this  opinion  before  the  Academy  of  Medicine,  I  picture  to 
myself  the  physicians  and  surgeons  present  at  the  meet- 
ing staring  at  him  over  their  spectacles  with  surprise 
and  uneasiness.  Nevertheless,  he  was  right,  and  this 
assertion,  daring  at  the  time,  was  a  first  victory  of  the 
laboratory  over  the  clinic. 

A  second  followed  straightway:  "In  the  puerperal 
infections,  the  pus  of  the  uterus,  that  of  the  peritoneum, 
and  the  blood-clots  in  the  veins  contain  a  microbe 
occurring  in  the  form  of  rounded  granules  arranged  in 
chains.  This  chaplet-like  aspect  is  especially  apparent 
in  the  cultures.  Pasteur  does  not  hesitate  to  declare 
that  this  microscopic  organism  is  the  most  frequent 
cause  of  infections  among  women  in  confinement.  One 
day,  in  a  discussion  on  puerperal  fever  at  the  Academy 
of  Medicine,  one  of  the  most  renowned  of  his  colleagues 
made  an  eloquent  dissertation  on  the  causes  of  epidemics 
in  the  maternity  hospitals.  Pasteur  from  his  place 
in  the  audience  interrupted  him:  'The  cause  of  the 
epidemic  is  nothing  of  the  kind  !  It  is  the  doctor  and 
his  staff  who  carry  the  microbe  from  a  sick  woman 
to  a  healthy  woman!'  And  when  the  orator  replied 
that  he  was  convinced  that  no  one  would  ever  find  this 


NEW   EXAMPLES    OF   PHYSIOLOGICAL    CONFLICTS    271 

microbe,  Pasteur  darted  to  the  blackboard  and  drew 
the  organism  with  its  chaplets,  saying:  'There!  There 
is  its  picture!'  His  conviction  was  so  strong  that  he 
could  not  refrain  from  expressing  it  forcibly.  One 
can  scarcely  understand  to-day  the  surprise,  and  the 
stupefaction,  even,  of  the  medical  men  and  their  students 
when  at  the  hospital,  with  a  simplicity  and  an  assurance 
which  seemed  presumptuous  in  a  man  who  was  entering, 
a  lying-in  hospital  for  the  first  time,  Pasteur  criticised 
the  methods  of  dressing  wounds,  and  declared  that  all 
bandages  should  be  placed  in  a  sterilizing  oven.  Further- 
more, he  maintained  that  he  could  tell  by  examination 
of  the  lochia,  which  women  would  have  an  attack  of 
puerperal  fever,  and  he  assured  them  that  in  a  woman 
who  was  very  badly  infected  he  could  demonstrate 
the  microbe  in  the  blood  of  the  finger.  And  he  was  as 
good  as  his  word.  In  spite  of  the  tyranny  exercised  by 
the  medical  education  which  weighed  heavily  at  that  time 
on  the  minds  of  the  students,  some  of  them  were  capti- 
vated and  came  to  the  laboratory  to  observe  at  closer 
range  those  methods  which  afforded  diagnoses  so  exact 
and  prognoses  so  sure."1 

I  will  cite  only  one  more  fact,  which  in  some  degree 
forms  a  connection  with  what  is  to  follow.  In  the  course 
of  this  search  for  microbes  which  has  been  so  fruitful, 
Pasteur  encounters  a  bacterium  which  cannot  develop 
under  the  skin  because  the  temperature  of  the  human 
body  is  a  little  too  high  for  it.  Immediately  his  thought 
reverts  to  the  anthrax  bacteridium  which  is  unable  to 
develop  in  birds,  and  he  asks  himself  if  this  does  not 
result  from  the  high  temperature  of  these  animals, 
which  is  always  in  the  neighborhood  of  42°C.  What 
would  happen  if  one  could  lower  the  temperature  of 

1  L'Œuvre  médicale  de  Pasteur,  par  le  Dr.  E.  Roux,  Agenda  du  chim- 
iste, 1896. 


272  pasteur:  the  history  of  a  mind 

an  inoculated  chicken  some  degrees?  The  success  of 
the  experiment  was  immediate.  A  chicken,  the  feet 
and  hind  quarters  of  which  were  plunged  into  water  at 
25°C,  so  that  the  temperature  of  its  whole  body  was 
lowered  to  37-38°C,  which  is  the  temperature  of  animals 
susceptible  to  anthrax,  died  of  this  disease,  although 
resistant  to  it  under  normal  conditions.  If  the  chicken 
is  taken  from  the  water  and  heated  at  the  time  when 
the  first  symptoms  of  invasion  of  the  tissues  appear, 
it  triumphs  over  all  the  parasites  and  recovers.  Later 
Gibier  made  the  reverse  experiment,  giving  anthrax 
to  frogs  which  are  not  susceptible  to  this  disease  because 
they  are  cold-blooded  animals,  the  body  temperature 
being  too  low.  To  accustom  them  little  by  little  to 
living  in  warm  water,  suffices  to  render  them  capable 
of  succumbing  to  anthrax  when  their  body  temperature 
has  been  thus  raised.  The  interpretation  of  these  two 
facts  is  less  simple  then  Pasteur  supposed  it  to  be  and 
we  shall  meet  them  again  very  soon  in  connection  with 
variations  in  virulence.  I  cite  them  only  as  further 
evidence  of  his  tendency  to  relegate  everything  as  much 
as  possible  to  the  domain  of  physics  and  chemistry, 
to  study,  in  the  light  of  these  two  sciences,  the  physio- 
logical properties  of  the  microbe  and  to  oppose  these 
properties  to  those  of  the  tissues. 

However  broad-minded  one  may  be,  he  is  always 
to  some  extent  the  slave  of  his  education  and  of  his  past. 
It  is  clear  that  Pasteur  inclined  naturally  to  the  side 
of  chemistry,  and  there  were  not  lacking  men  to  reproach 
him  for  this.  To  this  chiding  he  always  disdained  to 
respond.  Doubtless  he  thought  it  was  not  worth  while, 
and  that  he  must  be  content  to  pity  those  who  believed  it 
possible  for  a  vital  problem  to  be  something  other  than  a 
problem  of  physics  and  chemistry.  This  will  be  still  more 
evident  in  the  study  which  we  shall  make  of  virulence. 


PASTEUR 

(Int.  Med.  Congress  at  Copenhagen,  1884.) 

(Courtesy  of  Capt.  J.  C.  Pry  or,  Naval  Med.  School,  Washington, 

D.  C.) 


EIGHTH   PART 
The  Study  of  Viruses  and  Vaccines 

I 
MICROBIAL  DISEASES  AND  VIRUS  DISEASES 

What  idea  could  one  have,  about  1880,  of  virulence 
as  we  understand  it  to-day?  The  answer  is  easy  if  one 
is  willing  to  regard  it  from  the  point  of  view  of  our 
actual  knowledge.  Considerable  variation  in  virulence 
had  been  determined  in  various  microbial  diseases, 
but  it  was  not  known  whether  they  had  the  character 
of  the  virus  diseases,  that  is,  would  not  recur  in  the  same 
individual.  For  the  true  virus  diseases,  such  as  small- 
pox and  cowpox,  the  established  variations  in  virulence 
were  feeble,  and  supposed  to  be  dependent,  as  we  have 
seen,  on  external  conditions,  which  amounts  to  saying 
that  they  were  unexplained. 

This  point  of  view  shows  us  clearly  the  difficulties 
of  the  question,  but  it  is  not  from  this  standpoint  that 
our  observations  should  be  made.  What  could  one 
think  at  that  time  concerning  the  relation  between 
microbial  diseases  and  the  virus  diseases,  is  what 
we  must  ask  ourselves.  Strange  to  say,  one  thought 
nothing!  These  were  two  territories  separated  by  an 
arm  of  the  sea  over  which  there  was  no  bridge.  From 
one  of  the  continents  a  person  might  indeed  from  time 
to  time  glimpse  the  other  and  observe  its  outlines, 
but   both   seemed   isolated   and  equally  impenetrable. 

For  Pasteur  alone,  the  man  of  the  large  horizons, 
they   were   in   some   places   in   contact.     The   careful 

18  273 


274  pasteur:  the  history  of  a  mind 

reading  of  the  works  of  Jenner  and  his  followers  had 
left  a  profound  impression  on  the  mind  of  the  master, 
and  by  correlating  incessantly  in  his  thoughts  the 
teachings  of  the  books  and  those  of  the  laboratory,  he 
had  formed  a  general  impression  which  I  desire  to 
summarize,  relying  not  simply  on  my  own  recollections, 
but  also  on  that  of  his  collaborators  at  this  memorable 
time. 

On  the  subject  of  variation  in  power  of  microbes  to 
attack  there  existed  only  the  curious  results  obtained  by 
Coze  and  Feltz  in  1869,  confirmed  since  then  by  Davaine 
for  the  anthrax  bacteridium,  and  especially  for  the  dis- 
ease of  Leplat  and  Jaillard.  The  virus  increased  in 
strength  by  passage  through  the  organism.  The  blood 
of  the  first  animal  inoculated  was  fatal  to  a  second  only 
in  a  dose,  let  us  say,  of  one-tenth  of  a  drop.  The  fatal 
dose  decreased  little  by  little  with  successive  animal 
passages  to  that  of  a  hundredth,  a  thousandth,  a  millionth 
of  a  drop.  This  fact  was  the  only  one  of  its  kind.  It 
was  eminently  curious  and  suggestive.  It  would  have 
been  more  so  if  there  had  not  been  needed,  in 
order  to  realize  it,  the  cooperation  of  the  organism, 
at  cross  purposes  with  which  everything  becomes  ob- 
scure. Men  so  little  dreamed  of  ascribing  the  increased 
virulence  to  its  true  origin,  the  microbe  itself,  that  when 
Pasteur,  in  his  study  of  the  septic  vibrio,  finds  cultures 
which  prove  to  be  unequally  active  in  animals,  his  first 
thought  is  that  he  has  two  or  several  septic  vibrios  of 
unequal  virulence,  which  the  cultures  have  separated 
more  or  less  completely.  Under  this  impression  he 
carried  on  investigations  for  a  long  time  without  result. 
It  was  only  when  he  discovered  that  a  simple  change 
in  culture  method,  namely,  the  substitution  of  a  blood 
serum  slightly  charged  with  coagulated  fibrine  for  Liebig's 
bouillon,  suddenly  increased  the  virulence  of  a  vibrio 


MICROBIAL   DISEASE   AND   VIRUS   DISEASES  275 

which  for  20  or  30  generations  had  shown  itself  to  be 
attenuated,  that  he  accepted  the  idea  that  these  varia- 
tions depended  on  one  single  vibrio  and  its  culture 
medium. 

It  was  a  great  step  indeed;  but  beyond  this  there  was 
nothing,  and  in  order  to  see  farther  it  was  necessary 
to  consider  the  virus  diseases.  The  latter  presented 
facts  analogous  to  those  of  Coze  and  Feltz,  and  Davaine. 
It  was  known  that  there  were  benign  epidemics  of  smallpox 
and  others  that  were  deadly,  that  the  severity  was 
variable  in  the  course  of  the  same  epidemic,  and  generally 
diminished  as  it  drew  to  a  close.  It  was  also  known  from 
the  practise  of  smallpox  inoculation,  resorted  to  before  the 
time  of  Jenner,  that  inoculation  from  a  benign  case  of 
smallpox  ordinarily  produced  a  smallpox  still  more 
benign,  but  this  was  not  always  true,  for  sometimes 
the  inoculated  patient  died. 

The  vaccine  introduced  by  Jenner  had  been  a  wonder- 
ful discovery,  but  it  had  made  the  veil  still  thicker 
behind  which  the  virus  diseases  lay  concealed.  With 
it  variations  in  virulence  were  scarcely  to  be  feared. 
After  being  very  clearly  diminished  in  passing  from 
the  cow  to  the  man,  the  virulence  of  the  vaccine  was 
maintained  very  constantly  from  arm  to  arm,  for  a 
long  series  of  generations.  But  if  there  was  something 
immutable  in  the  severity  of  the  disease  or  in  its  period 
of  evolution,  there  was,  on  the  contrary,  great  variation 
in  the  duration  of  the  immunity  which  it  produced. 
So  that,  to  sum  up,  the  ideas  which  seem  to  us  to-day 
the  most  closely  related,  the  most  coherent,  were  at 
that  time  scattered  and  contradictory,  and  no  one 
attempted  to  correlate  them. 

It  is  here  that  Pasteur  experienced  the  benefit  of 
his  former  studies  and  of  facts  which  he  alone  knew, 
since  he  had  published  them  only  in  part,  and  in  that 


276  pasteur:  the  history  of  a  mind 

somewhat  dogmatic  style,  general  and  without  details, 
which  he  still  affected  at  this  time.  I  speak  of  his 
study  of  chicken  cholera,  concerning  which  I  have  as 
vet  said  only  a  word,  and  which  I  have  reserved  for 
the  following  chapter,  because  it  is  a  disease  which  has 
the  closest  analogies  with  the  virus  diseases.  We  shall 
see,  in  reality,  that  this  cholera,  like  smallpox,  is  some- 
times epidemic  and  deadly;  sometimes  chronic  and 
harmless;  that  transferred  from  the  chicken  to  the 
guinea-pig,  like  the  cowpox  transferred  from  the  cow 
to  the  man,  it  may  become  an  artificial  and  fixed  dis- 
ease, preserving  its  character  indefinitely. 


II 

CHICKEN  CHOLERA 

"Sometimes  there  breaks  out  in  the  poultry-yard  a 
disastrous  disease,  commonly  known  as  chicken  cholera. 
The  animal  which  is  a  prey  to  this  infection  is  without 
strength,  trembles  and  has  drooping  wings.  The  feath- 
ers of  the  body  are  ruffled  giving  it  the  form  of  a  ball; 
an  unconquerable  drowsiness  overpowers  it;  if  forced 
to  open  its  eyes  it  appears  to  waken  from  profound 
slumber;  soon  the  eyes  close  again,  and  in  most  cases, 
the  animal  does  not  change  its  position  until  death  comes, 
after  a  dumb  agony.  At  most  it  sometimes  shakes  its 
wings  for  a  few  seconds."1 

These  singular  symptoms  are  due  to  the  development 
of  a  microbe  which  can  be  isolated  in  cultures  in  neutral- 
ized chicken  bouillon.  Sowing  in  this  liquid  a  drop 
of  the  blood  of  a  chicken  which  had  died  of  the  cholera, 

1  Sur  le  choléra  des  poules.  Comptes  rendus  de  l'Académie  des 
Sciences,  1880. 


CHICKEN   CHOLERA 


277 


and  working  as  he  had  done  with  anthrax  blood,  Pasteur 
saw  develop  everwhere  small  non-motile  segments  of  an 
extreme  tenuity,  slightly  constricted  in  the  middle  (Fig. 
22),  and  clearly  approaching,  much  more  than  the  anthrax 
bacteridium  and  the  other  bacilli,  those  microscopic 
granules  to  which  Chauveau  had  attributed  the  active 
rôle  in  the  virulent  humors  of  cowpox,  smallpox,  and 
sheeppox. 


Fig.  22. 
Young. 


-Microbe  of  chicken  cholera. 


Old. 


This  organism  is  so  tenuous  that  the  precipitate  which 
it  forms  at  the  bottom  of  the  flask  is  sometimes 
almost  invisible;  it  appears  scarcely  to  touch  the  nutri- 
tive substances  placed  at  its  disposal,  and  one  might 
ask  himself  the  question  whether  it  changes  in  any 
respect  the  culture  fluid.  "Let  us  try,"  said  Pasteur 
to  himself;  and  he  tried,  and  saw  with  surprise  that  if 
this  bouillon  culture  was  filtered  by  passing  through 
a  porous  wall  in  order  to  remove  from  it  all  the  parasites, 
and  then  re-inoculated,   no  growth  took  place.     The 


278  pasteur:  the  history  of  a  mind 

first  culture  has  rendered  the  medium  unsuitable  for 
a  second,  as  the  first  attack  of  a  virus  disease  protects 
against  all  new  attacks.  Thus  was  sown  in  the  mind 
of  Pasteur,  a  seed  which  fell  on  good  ground  and  could 
not  fail  to  be  productive. 

Inoculation  with  this  organism  is  usually  fatal  but 
it  sometimes  happens  that  the  chicken,  after  having 
been  sick,  seems  to  recover.  Nevertheless  it  eats  little, 
its  comb  loses  color,  it  grows  thin,  and  finally  it  succumbs 
after  weeks  or  months  of  languor.  Is  it  always  the 
same  disease?  Yes,  for  the  organism  which  we  find 
in  the  tissues,  if  isolated,  kills  the  chickens  into  which 
it  is  inoculated.  Why,  then,  did  it  not  cause  the  death 
of  the  chicken  which  carried  it?  Whence  comes  this 
relative  immunity?  Pasteur  was  not  yet  able  to 
answer  this  question,  but  he  already  had  the  right  to 
put  it  to  himself.  While  waiting  to  find  the  solution, 
he  pointed  out  the  analogy  between  these  larval  forms 
of  the  cholera,  and  the  grave  and  often  incurable  forms 
of  certain  virus  diseases,  such  as  measles,  scarlatina, 
and  typhoid  fever. 

Many  ideas  are  already  knocking  at  the  portals  of 
his  mind:  and  this  is  not  the  end.  The  chicken  is  not 
the  only  domestic  animal  capable  of  offering  a  habitat 
to  the  microbe.  The  dog,  the  horse,  and  many  animals 
of  the  barnyard  are  also  inoculable.  The  rabbit  is 
particularly  susceptible,  and  Pasteur  discovered  later 
that  the  contagion  could  be  propagated  in  terriers. 
The  guinea-pig,  on  the  contrary,  is  quite  resistant. 
It  succumbs  to  inoculations  in  the  veins,  but  those 
under  the  skin  produce  scarcely  more  than  a  slight  abscess, 
which  bursts  spontaneously  and  heals  without  making 
the  animal  which  bears  it  appear  sick.  This  abscess 
is  a  kind  of  pure  culture  of  the  microbe,  and  if  we  inocu- 
late a  little  of  its  contents  into  chickens,  "  these  chickens 


CHICKEN   CHOLERA  279 

die  quickly,  while  the  guinea-pig  which  furnished  the 
virus,  recovers  without  the  least  suffering.  We  are 
present  here,  then,  at  a  restricted  evolution  of  a  micro- 
scopic organism  which  causes  the  formation  of  pus  and 
a  closed  abscess  without  bringing  about  any  internal 
disturbance  or  the  death  of  the  animal  on  which  it 
occurs,  and,  nevertheless,  one  which  is  always  ready  to 
convey  death  to  other  species  into  which  it  is  inoculated, 
ready  even  to  kill  the  animal  on  which  it  occurs  in  the 
form  of  an  abscess,  if  more  or  less  fortuitous  circum- 
stances enable  it  to  pass  into  the  blood  or  into  the 
splanchnic  organs. 

"Chickens  or  rabbits  which  live  in  the  company  of 
guinea-pigs  bearing  such  abscesses  may  suddenly  become 
sick  and  die  without  the  health  of  the  guinea-pigs  appear- 
ing to  be  in  the  least  impaired.  For  this  to  occur,  it 
is  only  necessary  that  the  abscesses  of  the  guinea-pigs 
should  rupture,  scattering  a  little  of  their  contents  on 
the  food  of  the  chickens  and  the  rabbits.  An  observ- 
ing person,  seeing  these  facts  and  ignorant  of  the  rela- 
tion of  which  I  am  speaking,  would  be  astonished  to  see 
chickens  and  rabbits  destroyed  without  any  apparent 
cause,  and  would  believe  that  the  disease  was  sponta- 
neous, for  he  would  be  far  from  supposing  that  it  had 
originated  in  the  guinea-pigs,  all  in  good  health,  especially 
if  he  knew  that  the  latter  are  also  subject  to  the  same 
disease.  How  many  mysteries  in  the  history  of  conta- 
gions will  some  day  receive  solutions  still  more  simple 
than  that  of  which  I  have  just  been  speaking!  Let 
us  reject  theories  which  we  can  contradict  by  convincing 
facts,  but  not  on  the  vain  pretext  that  certain  of 
their  applications  escape  us.  The  combinations  of 
nature  are  at  the  same  time  more  simple  and  more 
varied  than  those  of  our  imagination!" 

For  anyone  who  pondered  overJenner's  work,  what  was 


280  pasteur:  the  history  of  a  mind 

more  analogous  than  these  facts  with  what  was  known  on 
the  subject  of  those  apparently  spontaneous  sudden 
appearances  on  the  horse,  on  the  cow,  on  the  hands  of  the 
milkers,  that  is,  those  eruptions  of  horsepox,  of  cowpox, 
and  of  vaccinia?  What  more  natural  than  to  see  in 
smallpox  and  vaccinia  different  manifestations  of  the 
presence  of  the  same  microbe,  or  at  least  of  two  closely 
related  microbes?  In  all  these  cases,  the  ideas  regarding 
microbial  diseases  and  those  concerning  virus  diseases 
are  more  and  more  bound  together.  Pasteur  has  just 
spoken  of  the  imagination.  He  had  much  of  it,  and  he 
allowed  it  to  have  full  play  on  this  subject.  He  did 
not  even  scorn  the  dream.  "I  take  the  liberty"  he 
said  one  day,  "of  recalling  to  my  confrère,  M.  Blanchard, 
that  the  illusions  of  an  experimenter  form  a  great  part 
of  his  power.  These  are4he  preconceived  ideas  which 
serve  to  guide  him.  Many  of  them  vanish  in  the  long 
path  which  he  must  travel,  but  one  fine  day  he  discovers 
and  proves  that  some  of  them  are  adequate  to  the  truth. 
Then  he  finds  himself  master  of  facts  and  of  new  prin- 
ciples, the  applications  of  which,  sooner  or  later,  bestow 
their  benefits."1 

The  hour  had  come  for  him  to  enter  the  enchanted 
grotto  full  of  treasures. 


Ill 
DISCOVERY  OF  VACCINES 

The  first  experiments  on  chicken  cholera  date  from 
1879.  Interrupted  by  vacations,  they  had  been  resumed, 
but  were  upset  at  once  by  an  unforeseen  obstacle.  Al- 
most all  the  cultures  left  in  the  laboratory  had  become 
sterile. 

1  Comptes  rendus  de  l'Académie  des  Sciences,  1er  sem.,  1880. 


DISCOVERY   OF  VACCINES  281 

As  all  these  belonged  to  the  experiments  under  way, 
an  attempt  was  made  to  revive  them,  and  with  that 
end  in  view,  transfers  were  made  from  them  either  into 
chicken  bouillon  or  into  chickens.  Many  of  these  made 
no  growth,  and  also  spared  and  left  unimpaired  the 
animals  into  which  they  were  inoculated,  and  we  were 
about  to  throw  them  away,  in  order  to  begin  anew,  when 
it  occurred  to  Pasteur  to  inoculate  a  fresh  young  culture 
into  these  chickens  which,  at  least  in  appearance,  had 
so  well  resisted  the  inoculations  with  the  cultures 
made  the  preceding  summer. 

To  the  surprise  of  all,  perhaps  even  of  Pasteur  him- 
self, who  did  not  expect  such  a  success,  almost  all  of  these 
chickens  resisted,  whereas  new  chickens,  just  brought 
from  the  market,  succumbed  in  the  ordinary  length  of 
time,  thus  showing  that  the  culture  used  for  the  inocu- 
lation was  very  active.  With  one  blow,  chicken  cholera 
passed  to  the  list  of  virus  diseases  and  vaccination  was 
discovered!  What  secret  instinct,  what  spirit  of  divin- 
ation impelled  Pasteur  to  knock  at  this  door,  which 
was  only  waiting  to  be  opened?  Here  we  see  clearly 
the  part  played  by  his  readings  and  his  former  studies, 
by  the  incessant  ponderings  which  had  been  going  on 
in  his  mind,  and  by  the  intervention,  in  the  midst  of 
th^se  obscurities,  of  this  faculty  of  imagination  to  which 
he  has  referred  in  the  lines  that  precede,  lines  written 
just  at  the  time  when  he  was  setting  forth,  a  conqueror, 
in  the  realm  of  his  dream. 

He  had,  in  reality,  just  established  between  certain 
microbial  diseases  and  the  virus  diseases  a  definite 
connection  which  it  was  to  be  the  task  of  the  future 
to  enlarge  and  consolidate.  There  were,  then,  microbial 
diseases  which  did  not  recur!  One  could,  therefore, 
prepare  vaccines  insuring  protection  against  a  viru- 
lent   inoculation!     Prudently,    Pasteur  refrained  from 


282  pasteur:  the  history  of  a  mind 

saying  how  he  obtained  this  vaccine.  He  preferred  to 
insert  in  the  Note  in  which  he  announced  the  preceding 
fact,  another  fact  not  less  astonishing,  to  wit,  that  this 
vaccine,  once  developed,  could  be  reproduced  indefinitely 
by  cultures,  with  all  its  vaccinal  properties,  or  with  what 
has  since  been  called  its  degree  of  attenuation. 

If  one  can  say,  strictly  speaking,  that  Pasteur  had 
had  a  presentiment  of  the  first  of  these  facts,  the  latter 
at  least  was  entirely  unforeseen.  It  is,  or  seems  to  us 
at  least,  entirely  independent  of  the  other,  and  it  is 
possible  that  vaccination  would  still  be  in  force  even 
if  the  latter  did  not  exist.  But  it  was  none  the  less 
valuable  in  practice,  and  Pasteur  in  running  across  it 
must  have  recalled  the  history  of  Jenner,  and  even 
have  re-lived  it.     And  here  is  my  reason  ! 

It  is  well  known  that  Jenner,  after  having  discovered 
that  inoculation  with  cowpox  gave  protection  against 
smallpox  and  became  a  vaccine,  had  had  some  anxiety 
regarding  it.  He  feared,  in  the  first  place,  being  obliged  to 
return  to  the  cow  and  to  the  cowpox  to  obtain  his  vaccine, 
and  this  prospect  was  scarcely  calculated  to  please 
him.  According  to  his  idea,  cowpox  was  inoculated 
into  the  cow  by  a  milker  affected  with  smallpox,  was 
found  only  in  the  female  and  at  the  points  touched  by 
the  milker,  that  is  on  the  udder,  and  represented  con- 
sequently the  bovine  form  of  human  smallpox.  If  this 
were  so,  there  must  be  smallpox  in  order  to  produce 
cowpox,  and  as,  theoretically,  the  vaccine  suppressed 
the  smallpox,  here  was  a  vicious  circle.  Jenner  sought, 
therefore,  with  an  emotion  of  which  we  find  traces  in 
his  memoirs,  to  obtain  from  man  the  material  for  inocu- 
lation, the  vaccine,  to  vaccinate  from  arm  to  arm,  and 
he  succeeded.  It  was  his  chief  discovery,  and  one  which 
makes  for  his  eternal  glory.  But  the  same  history 
repeated  itself  in  Pasteur  nearly  a  century  later  and 


DISCOVERY   OF  VACCINES  283 

there  was  this  further  resemblance  that  the  absolute 
conservation  of  the  virulence  was  realized  neither  by  the 
vaccine  transferred  from  arm  to  arm,  as  Jenner  believed, 
nor  by  the  chicken  cholera  vaccine,  transferrd  from 
culture  to  culture,  as  Pasteur  believed.  In  both  cases, 
there  is  a  deterioration,  but  a  very  slow  one,  which  it 
has  required  years  to  perceive. 

In  any  event,  a  new  world  was  opened  to  him,  and 
he  must  push  on  into  it  eagerly.  This  is  what  Pasteur 
did  with  the  incomparable  authority  of  a  master,  con- 
stantly guided,  it  is  true,  by  the  then  prevailing  notions 
regarding  virus  diseases,  but  having  as  a  means  of  illumi- 
nating his  every  step  those  methods  for  cultivating 
the  virus  which  were  entirely  his  own.  I  have  no  inten- 
tion of  following  up  his  study  of  chicken  cholera;  I 
should  like,  merely,  to  point  out  the  principal  facts, 
those  which  should  not  be  forgotten  because  they  tell 
us,  in  a  particularly  simple  case  and  one  which  has  been 
well  worked  out,  what  a  virus  disease  really  is. 

If  we  inject  a  few  drops  of  a  young  culture  of  the 
microbe  of  chicken  cholera  into  one  of  the  large  pectoral 
muscles  of  a  chicken,  or  inject  them  into  its  blood,  or 
still  better,  put  them  on  the  food,  on  the  bread  or  the 
meat,  we  shall  see,  after  a  time  varying  with  the  path 
of  entrance,  the  symptoms  of  the  disease  appear  in  this 
fowl.  The  animal  loses  its  appetite,  becomes  drowsy, 
ruffles  itself  into  a  ball  and  dies  sometimes  in  24  hours, 
entirely  invaded  by  the  microbe,  which  is  found  in  its 
blood  and  in  all  its  organs. 

Instead  of  using  a  young  culture  for  inoculation,  let 
us  repeat  the  experiment  with  a  culture  several  weeks 
old.  We  shall  still  have  a  disease  marked  by  loss  of 
appetite,  drowsiness,  and  ruffled  feathers,  but  the  chicken 
does  not  die.  After  some  days  of  more  or  less  severe 
illness,  it  apparently  fully  recovers.     There  has  been, 


284  pasteur:  the  history  of  a  mind 

however,  a  development  of  the  microbe,  since  there 
has  been  disease,  and,  in  reality,  when  this  disease  is 
in  progress,  the  organism  can  be  found  at  the  point  of 
inoculation  and  in  all  the  tissues,  but  this  time  it  has 
not  caused  death.     The  chicken  has  repelled  the  attack. 

Has,  then,  this  benign  cholera  played  in  the  chicken 
the  rôle  of  the  benign  smallpox  or  vaccine  in  man?  Yes, 
for  this  chicken  is  henceforth  immune  to  inoculation  with 
the  youngest  and  most  virulent  culture  of  the  micrococcus. 
It  has  been  vaccinated  against  the  cholera. 

Let  us  continue  this  study  which  has  already  proved 
so  fruitful.  Since  the  power  of  action  on  the  organism 
diminishes  with  the  age  of  the  culture,  let  us  make 
our  inoculation  from  a  very  old  culture,  one  which  is 
near  the  point  of  death.  The  microbe,  still  alive,  can 
still  cloud  the  bouillon  into  which  it  is  sown.  It  does 
this  slowly,  but  life  and  virulence  are  not  synony- 
mous in  this  case,  for  the  organism  is  absolutely  incapable 
of  developing  in  the  body  of  a  chicken,  or  communi- 
cating to  it  even  the  slightest  disease.  Here  it  is  the 
chicken  which  overcomes  and  kills  the  inoculated  microbe 
straightway.  The  latter,  in  spite  of  its  specific  origin, 
entirely  resembles,  therefore,  those  thousands  of  spe- 
cies of  micrococcus  which  are  met  with  everywhere  on 
the  surface  of  the  body,  which  fill  the  intestinal  canal, 
and  which  are  always  harmless.  It  is,  nevertheless, 
that  same  microbe  which  some  weeks  before  killed  ten 
chickens  out  of  ten.  A  virus,  then,  is  not  that  entity, 
not  that  unity,  which  it  was  considered  to  be  by  the 
old  physicians.  It  is  in  a  state  of  perpetual  evolution, 
of  continuous  variation,  due  to  wholly  natural  causes. 

Let  us  take,  now,  this  last  chicken  which  suffered  no 
inconvenience  from  the  inoculation  with  our  dying 
virus,  and  let  us  try  to  inoculate  it  with  the  virulent 
virus;  it  behaves  toward  this  exactly  as  a  new  chicken 


DISCOVERY   OF  VACCINES 


285 


would;  it  dies,  or  at  least  is  very  sick,  the  extent  of  the 
disease  and  the  danger  of  death  being  in  inverse  ratio 
to  the  amount  it  had  suffered  in  the  previous  inocula- 
tion, for  the  slightest  disease  produced  by  inoculation 
serves  as  some  protection. 

Instead  of  making  the  three  experiments  which  pre- 
cede, we  might,  clearly,  arrange  a  greater  number 
extending  over  the  period  of  life  of  the  virus,  six,  ten, 
etc.,  in  other  words,  interpose  between  the  most  sensi- 
tive animal  and  the  most  resistant,  a  whole  series  of 
animals  differing  in  degree  of  immunity,  each  one  of 
which  will  acquire  a  degree  of  immunity  corresponding 
to  the  amount  of  vaccine  which  it  can  endure  without 
dying.  The  more  severe  the  disease  the  greater  the 
protection  the  disease  will  afford  it. 

All  these  animals,  identical  in  appearance,  different 
in  reality,  clearly  behave  in  a  very  different  manner 
toward  the  same  microbe  of  virulent  cholera.  Some, 
vaccinated,  resist  it  without  any  trouble.  Others,  little 
vaccinated  or  only  recently,  will  become  sick  or  die. 
Furthermore,  an  animal,  vaccinated  or  not,  behaves 
very  differently  toward  microbes  of  unequal  attenua- 
tion. It  is  the  variable  result  in  this  conflict  which 
makes  the  variety  of  pathological  cases,  and  there  are 
not  on  the  palette  of  any  painter  colors  enough  to  des- 
ignate the  innumerable  differences  in  receptivity  which 
we  find  in  the  virulent  diseases. 


IV 
ANTHRAX  IS  ALSO  A  VIRUS  DISEASE 

As  the  study  of  chicken  cholera  progressed  Pasteur 
devoted  much  thought  to  anthrax  on  which  he  was  work- 
ing at  the  same  time.     He  wished  to  study  its  etiology,  to 


286  pasteur:  the  history  of  a  mind 

determine  precisely  the  means  by  which  the  bacteri- 
dium  passes  from  one  animal  to  another,  to  discover 
how  the  disease  can  be  at  the  same  time  endemic  and 
epidemic,  can  have  more  or  less  periodic  awakenings, 
or  lie  dormant  for  long  years.  Koch  had  already  out- 
lined this  subject,  and  Pasteur  had  to  content  himself 
with  adding  the  finishing  touches,  but  these  touches 
are  the  work  of  a  master.  We  shall  be  thoroughly 
convinced  of  that  when  we  note  the  principal  facts. 
Koch  had  shown  how  the  spores  are  formed  when  an 
animal,  dead  of  anthrax,  is  buried,  but  he  had  never 
found  them  in  the  earth,  nor  did  he  know  how  long 
they  lived  there.  Pasteur  succeeded  at  the  outset  in 
isolating  the  bacteridium  of  anthrax  from  the  myriads 
of  germs  which  accompany  it  in  the  soil,  always  employ- 
ing for  this  purpose  the  same  method:  that  of  pure 
cultures  in  the  medium  best  fitted  to  the  physiological 
needs  of  the  anthrax  bacillus.  These  experiments 
date  from  1881.  The  method  of  making  cultures  on 
solid  media,  conceived  by  Koch,  was  not  yet  known  in 
the  laboratory,  having  been  published  only  that  year.  It 
would  certainly  have  simplified  the  problem  and  facil- 
itated the  researches,  but  we  see,  as  has  since  been 
admitted,  that  it  was  not  indispensable  for  studies  of 
this  kind,  and  that  Pasteur  extricated  himself  from 
his  difficulties  without  it.  It  is  true  that  another  would 
probably  have  failed. 

Thanks  to  this  method,  Pasteur  discovers  that  the 
anthrax  spores  can  persist  a  long  time  in  the  vicinity 
of  the  place  of  burial,  and  that  they  can  be  found  there 
after  a  period  of  12  years,  as  virulent  as  on  the  first  day. 
This  gave  birth  to  a  new  problem.  How  can  these 
spores  on  the  soil  of  the  burial  pit  resist  the  rain  which 
engulfs  them,  the  wind  which  sweeps  them  away,  and, 
we  should  add,  to-day,  the  light  of  the  sun,  which  is  more 


ANTHRAX   IS   ALSO   A  VIRUS   DISEASE  287 

active  on  them  than  its  heat.  This  might  be  conceived 
as  due  to  intermittent  cultures  which  renew  and  multiply 
the  spores,  but  there  is  no  probability  in  such  an 
explanation,  the  soil,  rich  in  vegetable  matter,  being 
full  of  organisms  which  are  much  better  prepared 
than  the  anthrax  bacteridium  to  profit  by  the  slightest 
condition  favorable  to  bacterial  growth.  Pasteur  was 
seeking  an  explanation  in  some  other  direction,  but  he 
knew  not  where.  The  solution  came  to  him  by  intuition 
one  day,  in  the  course  of  a  walk.  "It  was  after  the 
harvest;  there  remained  only  the  stubble.  The  atten- 
tion of  Pasteur  was  drawn  to  a  portion  of  the  field  be- 
cause of  the  difference  in  the  color  of  the  soil.  The 
owner  explained  that  some  sheep  which  had  died  of 
anthrax  had  been  buried  there  the  preceding  year. 
Pasteur,  who  always  investigated  things  very  closely, 
observed  on  the  surface  of  the  soil  a  multitude  of  the 
tiny  castings  of  earthworms.  The  idea  occurred  to 
him  then  that  in  their  continual  journeys  from  the 
depths  to  the  surface,  the  worms  brought  with  them  soil 
rich  in  the  humus  which  surrounds  the  carcass  of  the 
animal,  and  with  it  the  anthrax  spores  which  it  contains. 
.  .  .  Pasteur  never  stopped  with  theories;  he  imme- 
diately proceeded  to  experimental  work.  The  latter 
justified  his  suppositions,  the  earth  from  one  of  the 
worms  when  inoculated  into  guinea-pigs  gave  them 
anthrax."1 

These  spores,  brought  to  the  surface  of  the  soil  in 
this  way,  contaminate  vegetation  and  reach  by  way  of 
food  and  drink  the  digestive  canal  of  the  farm  animals. 
Sheep  which  are  kept  over  the  spot  where  a  victim  of 
anthrax  is  buried,  easily  contract  anthrax,  especially  if 
their  food  contains  chaff,  stubble,  awns,  or  small  prickly 

1  L'Œuvre  médicale  de  Pasteur,  par  le  Dr.  E.  Roux,  Agenda  du  chimiste, 
1896. 


288  pasteur:  the  history  of  a  mind 

or  sharp  substances,  capable  of  injuring  in  places  the 
epidermis  of  the  intestinal  canal,  and  of  thus  breaking 
the  natural  barrier  opposed  to  the  invasion  of  the  germs. 
The  symptoms  of  the  disease  thus  provoked  are  those 
of  the  disease  as  it  occurs  naturally,  so  that,  as  Koch 
had  conjectured,  it  is  especially  through  the  food  that 
contagion  takes  place.  And  it  is  thus  that  the  disease 
may  be  at  the  same  time  endemic  and  epidemic,  and 
may  render  certain  regions  and  certain  fields  dangerous, 
without  causing  any  trouble  in  their  vicinity. 

All  these  researches,  as  the  reader  divines,  had  been 
carried  on  for  the  sake  of  establishing  a  prophylaxis 
for  anthrax,  and  already  a  certain  number  of  practical 
conclusions  could  be  drawn  regarding  precautions  to 
be  taken  in  burying  an  animal  affected  with  anthrax. 
These  were  abruptly  broken  off  as  soon  as  there  ap- 
peared the  first  intimations  of  the  possibility  of  a  vaccina- 
tion for  anthrax.  Was,  then,  anthrax  also  a  virus 
disease,  not  prone  to  recur? 

This  question  was  solved  for  Pasteur  as  soon  as  it 
was  stated.  Furthermore,  his  solution  was  published 
without  anyone's  having  observed  it  in  the  Note  in 
which  it  was  inserted.  In  this  Note  of  July  12,  1880, 1 
devoted  to  the  etiology  of  anthrax,  Pasteur  had  in 
reality  introduced,  almost  in  parenthesis,  and  without 
explaining  at  all  its  place  in  this  question,  a  phrase  in 
which  he  had  incidentally  pointed  out  this  fact  :  When 
8  sheep,  which  had  been  subjected  to  a  prolonged  so- 
journ on  a  spot  where  an  anthrax  victim  had  been  buried 
and  had  proved  resistant,  were  inoculated  at  the  close 
of  the  experiment  with  a  culture  of  virulent  anthrax, 
several  of  them  survived,  whereas  fresh  sheep  of  the  same 
race  succumbed  almost  without  exception  to  the  same  in- 

1  Sur  Pétiologie  du  charbon  (en  collaboration  avec  MM.  Chamberland 
et  Roux).    Comptes  rendus  de  l'Ac.  des  Sciences,  t.  XCI,  1880,  p.  86. 


ANTHRAX   IS   ALSO   A  VIRUS   DISEASE  289 

oculation.  This  fact  had  remained  in  the  mind  of  Pasteur 
as  a  question,  and  he  had  believed  that  he  could  solve  it. 
Afterwards,  calling  to  mind  that  chickens,  fed  upon  food 
contaminated  by  the  cholera  organism,  do  not  always  die 
and  are  sometimes  found  to  be  vaccinated  when  they 
survive,  he  had  asked  himself  if  the  sheep  in  the  preceding 
experiment  had  not  acquired  their  immunity  through  a 
former  contagion  caused  by  food.  But  then,  according 
to  this  hypothesis,  anthrax  was  a  disease  which  would 
not  recur. 

Later  something  else  occurred  to  confirm  him  in  this 
idea.  In  a  series  of  experiments  made  with  Chamber- 
land  in  the  Jura,1  in  order  to  test  the  value  of  a  cure 
for  anthrax,  he  had  had  the  opportunity  of  seeing  two 
cows  become  very  sick  as  the  result  of  a  trial  inoculation, 
but,  having  resisted,  endure  without  any  apparent 
difficulty  a  virulent  inoculation  which  made  very  ill 
or  even  killed  fresh  animals  not  previously  prepared. 

All  this  proved  to  Pasteur  that  anthrax  was  a  virus 
disease,  and  now  the  only  question  was  how  to  find  its 
vaccine.  Naturally,  he  turned  first  to  the  method 
which  had  been  successful  with  chicken  cholera,  and 
tried  to  let  the  bacillus  become  old  in  its  culture  me- 
dium. But  immediately  a  difficulty  arose,  that  is,  the 
anthrax  bacillus  very  quickly  transformed  itself  into 
spores,  and  the  spore  does  not  grow  old;  the  spore  is  a 
'  '  seed, '  '  and  for  a  seed,  time  is  almost  suspended. 2     It  was, 

1  Sur  la  non  récidive  de  l'affection  charbonneuse  (en  collaboration 
avec  M.  Chamberland).     Co.  rend,  de  T Ac.  des  Sri.,  t.  XCI,  1880,  p.  533: 

2  It  is  not  known  how  long  seeds  or  spores  will  live  under  favorable 
conditions.  Dr.  W.  J.  Beal  buried  25  varieties  of  weed-seeds  in  sandy 
soil  in  bottles  of  earth,  mouth  down,  and  found  some  individuals  of 
11  varieties  alive  after  25  years,  but  they  germinated  very  irregularly. 
The  senior  writer  put  spores  of  the  hay-bacillus  into  concentrated 
glycerin,  exposed  to  the  air  in  a  cotton-plugged  test  tube,  10  years  ago 
and  a  very  few  are  still  living.     Trs. 

19 


290  pasteur:  the  history  o-f  a  mind 

therefore,  necessary  to  prevent  spores  from  forming, 
at  the  same  time  keeping  the  bacillus  alive.  This  can 
be  accomplished  in  different  ways,  the  first  successful 
method  being  the  use  of  antiseptics.  That  did  not 
satisfy  Pasteur.  He  wished  a  second  edition  of  the 
chicken  cholera.  He  searched  in  another  direction 
and  finally  discovered  that  it  sufficed  to  keep  the  culture 
in  a  shallow  layer  of  neutral  chicken  bouillon  at  42-43°  C. 

We  then  see  reproduced  the  same  phenomena  as  in 
chicken  cholera.  After  a  month  passed  under  these 
conditions,  a  little  extreme  as  to  temperature,  the  bac- 
teridium  is  dead,  that  is  to  say,  the  best  culture  medium 
inoculated  with  it  remains  sterile.  After  8  days,  cultures 
are  still  made  from  it  readily  and  give  abundant  growth, 
but  the  organism  is  harmless  to  the  guinea-pig,  the 
rabbit,  and  the  sheep,  three  species  most  susceptible 
to  anthrax.  Before  the  virulence  is  lost,  it  passes  in 
the  course  of  about  a  week  through  all  degrees  of  atten- 
uation, and,  as  in  the  case  of  the  chicken  cholera  organ- 
ism, each  of  these  grades  of  attenuated  virulence  may  be 
indefinitely  preserved  through  cultures.  Thus  vaccines 
were  created.  Nothing  is  easier  than  to  find  in  these 
graded  viruses  the  means  of  giving  to  sheep,  cows,  and 
horses  a  benign  fever,  capable  of  preserving  them  after- 
wards from  the  fatal  disease. 

These  vaccines  had  in  this  respect  a  practical  impor- 
tance very  much  greater  than  those  of  chicken  cholera. 
The  victims  of  anthrax  were  counted  by  thousands  in 
France  alone,  and  the  losses  were  reckoned  in  millions. 
Anthrax  vaccination  could  remedy  all  this  but  before 
bringing  about  its  acceptance,  what  trouble,  what  time, 
what  efforts  to  convince  the  public,  the  veterinarians 
and  the  farmers!  Here  it  is  that  we  shall  find  again 
Pasteur  the  apostle,  whom  we  have  seen  in  action 
after  his   studies   on   the   silkworm,    the  Pasteur  who 


ANTHRAX   IS   ALSO   A  VIRUS   DISEASE  291 

would  have  wished  to  be  everywhere,  to  see  every- 
thing, and  to  rely  on  no  one.  He  had  opened  the  cam- 
paign in  an  almost  startling  manner  with  that  famous 
experiment  at  Pouilly-le-Fort,  which  so  impressed  every- 
body. I  shall  borrow  the  account  from  M.  Roux,  who 
saw  it  and  collaborated  in  it. 

"The  Society  of  Agriculture  of  Melun  had  proposed 
to  Pasteur  a  public  trial  of  the  new  method.  The  pro- 
gram was  arranged  for  the  28th  of  April,  1881. 
Chamberland  and  I  were  away  on  a  vacation.  Pasteur 
wrote  to  us  to  return  immediately,  and  when  we  were 
reunited  in  the  laboratory  he  told  us  what  had  been 
agreed  upon.  Twenty-five  sheep  were  to  be  vaccinated, 
and  then  inoculated  with  anthrax;  at  the  same  time  25 
other  sheep  would  be  inoculated  as  checks;  the  first 
would  resist;  the  second  would  die  of  anthrax.  The 
terms  were  exact;  no  allowance  was  made  for  contin- 
gencies. When  we  remarked  that  the  program  was 
severe,  but  that  there  was  nothing  to  do  except  carry 
it  out  since  he  had  agreed  to  it,  Pasteur  replied: 
'What  succeeded  with  14  sheep  in  the  laboratory 
will  succeed  with  50  in  Melun.  ' 

"The  animals  were  collected  at  Pouilly-le-Fort,  near 
Melun,  on  the  property  of  M.  Rossignol,  a  veterinarian 
who  originated  the  idea  of  the  experiment  and  who  was 
to  watch  it.  'Be  sure  not  to  make  a  mistake  in  the 
bottles,'  said  Pasteur  gaily,  when  on  the  fifth  of  May, 
we  were  leaving  the  laboratory  in  order  to  make  the 
first  inoculations  with  the  vaccine. 

"A  second  vaccination  was  made  on  the  17th  of  May, 
and  every  day  Chamberland  and  I  would  go  to  visit 
the  animals.  On  these  repeated  journeys  from  Melun 
to  Pouilly-le-Fort,  many  comments  were  overheard, 
which  showed  that  belief  in  our  success  was  not  universal. 
Farmers,  veterinarians,    doctors,    followed   the   experi- 


292  pasteur:  the  history  op  a  mind 

ment   with   active   interest,    some   even   with   passion. 
In  1881  the  science  of  microbes  had  scarcely  any  parti- 
sans; many  thought  that  the  new  doctrines  were  baleful, 
and  regarded  it  as  an  unexpected  piece  of  good  fortune 
that  had  drawn  Pasteur  and  his  staff  out  of  the  labora- 
tory to  be  confounded  in  the  broad  daylight  of  a  public 
experiment.     They  were    going    then    with    one    blow 
to  put  an  end  to  these  innovations,  so  compromising  to 
medicine,  and  to  find  again  security  in  the  same  tradi- 
tions and  ancient  practices,  for  a  moment  threatened! 
"In  spite  of  all  the  excitment  aroused  by  it,   the 
experiment  followed  its  course;  the  trial  inoculations 
were  made  the  31st  of  May,  and  the  rendezvous  was 
appointed  for  the  second  of  June  to  determine  the  result. 
Twenty-four  hours  before  the  time  decided  upon,  Pasteur, 
who  had  rushed  into  the  public  experiment  with  such  per- 
fect confidence,  began  to  regret  his  audacity.     For  some 
moments  his  faith  was  shaken,  as  though  he  feared  the 
experimental  method  might  betray  him.     A  mental  ten- 
sion too  long  continued  had  brought  about  this  reaction, 
which,  however,  did  not  last  long.     The  next  day,  more 
assured  than  ever,  Pasteur  went  to  verify  the  brilliant 
success  which  he  had  predicted.     In  the  multitude  which 
thronged  that  day  at   Pouilly-le-Fort,  there  were  no 
longer  any  who  were  incredulous;  only  admirers." 

This  fine  success1  did  not  immediately  bring  convic- 
tion. He  had  to  repeat  the  experiment  in  different 
places  in  France  and  abroad,  in  order  to  convince  those 
who  wished  to  touch  and  to  see  before  believing.  Noth- 
ing can  give  an  idea  of  the  activity  of  Pasteur  at  this 
time.     To  the  life  within  the  laboratory,  which  continued 

1  Fourteen  days  after  the  second  vaccination  the  50  animals  were  in- 
oculated, all  in  the  same  way  from  the  same  virulent  culture,  and  2  days 
later,  as  Pasteur  had  predicted,  the  25  vaccinated  animals  were  unharmed 
and  the  25  unvaccinated  animals  were  dead.     TVs. 


ANTHRAX   IS   ALSO   A  VIRUS   DISEASE  293 

at  full  flood,  and  where  studies  on  rabies  had  already 
commenced,  was  now  added  a  public  life  not  less  active. 
He  must  superintend  the  manufacture  and  the  sending 
out  of  the  vaccine  wherever  public  or  private  experiments 
were  made,  must  inquire  into  the  results,  details  of 
which  were  never  given  in  sufficient  number  or  pre- 
cisely enough,  must  reply  to  the  demands  for  information, 
to  the  fears  which  preceded  an  experiment,  to  the  com- 
plaints which  sometimes  followed  it.  Pasteur  carried 
on  almost  all  this  correspondence  himself.  He  must 
also  reply  to  criticisms  and  to  sly  attacks  as  well  as 
to  those  of  open  war.  Nor  were  his  adversaries  confined 
to  France.  Koch  and  his  pupil,  Loffler,  for  example, 
had  published  against  the  theory  and  practice  of  vaccina- 
tion some  awkward  and  fruitless  criticisms,  which  they 
must  regret  to-day.  In  this  continual  strife,  Bouley 
made  himself  the  champion  of  Pasteur  and  devoted 
his  whole  spirit  to  the  task. 

Thanks  to  these  prodigious  efforts,  thanks  to  the 
precision  of  the  results,  the  practice  of  vaccination 
quickly  became  the  custom,  and  when  publishing,  in 
1894,  in  the  Annales  de  l'Institut  Pasteur,  the  statistics 
on  anthrax  vaccination  on  sheep  and  cattle,  M.  Chamber- 
land  was  able  to  state,  that  in  the  case  of  the  former 
a  total  of  3,400,000  animals  had  been  vaccinated  in 
10  years  with  a  mortality  of  less  than  1  per  cent  ;  in  the 
case  of  the  second,  a  total  of  438,000  had  been  vacci- 
nated with  a  mortality  of  about  3  per  thousand.  Finally, 
he  estimated  the  beneficial  results  for  French  agriculture 
from  the  use  of  vaccines  at  5,000,000  francs  for  sheep, 
and  2,000,000  francs  for  cattle.  It  is  evident  that  if 
the  laboratory  had  been  laboriously  painstaking,  it  was 
not  labor  lost.  It  is  anthrax  vaccination  that  first 
spread  through  the  public  mind  faith  in  the  science  of 
microbes. 


294  pasteur:  the  history  of  a  mind 

V 
STUDIES  ON  RABIES 

Although  it  was  these  experiments  at  Pouilly-le- 
Fort  and  the  anthrax  vaccinations  which  first  overcame 
the  general  scepticism  regarding  the  new  doctrines, 
it' was  the  prophylaxis  for  rabies  which  gave  them  the 
great  place  in  public  confidence  which  they  now  enjoy. 
We  cannot  fail  to  recognize  that,  from  this  point  of  view, 
this  disease  was  well  chosen.  It  has,  fundamentally, 
no  importance.  The  mortality  which  it  causes  is  slight. 
Man  can  protect  himself  from  it  without  any  scientific 
apparatus,  simply  by  police  measures,  as  is  done  in 
Germany,  and  that  country  may  well  scoff  at  us,  since 
without  any  Institute  for  fighting  rabies,  she  had  less 
deaths  from  it  throughout  the  whole  empire  than  we 
have  in  Paris.  But  rabies  has  a  hold  on  the  public 
imagination;  it  evokes  legendary  visions  of  raging 
victims,  inspiring  terror  in  all  those  in  their  vicinity, 
bound  and  howling,  or  asphyxiated  between  two 
mattresses. 

The  reality  is  much  more  simple  and  calm,  and  few 
deaths  are  more  peaceful  than  certain  deaths  from 
rabies,  but  it  was  easy  to  foresee  that  a  victory  over  this 
disease  would  be  reckoned  none  the  less  as  a  great  one. 
Only  it  did  not  seem  easy.  In  the  first  place,  while  rabies 
might  pass  with  the  public  for  a  virus  disease,  it  had  not 
that  character  for  the  physician  or  the  surgeon,  because 
every  man  and  every  animal  that  contracted  it  died 
from  it,  and  it  was  consequently  impossible  to  know 
whether  it  would  recur  in  the  same  individual.  In  the 
second  place,  the  only  means  of  transmitting  it  was  by 
having  a  mad  animal  bite  another  animal,  or  by 
inoculating  it  with  saliva  from  a  rabid  animal,  but  this 


PASTEUR   STUDYING  RABIES 

(From  the  painting  by  Edelfelt.) 


STUDIES   ON   RABIES  295 

method  of  transmission  was  most  uncertain.  The 
incubation  period  for  rabies  is  extremely  variable; 
it  may  be  some  days  or  it  may  be  several  months. 
Nothing  is  more  unendurable  for  an  experimenter  than 
these  long  and  uncertain  delays  between  an  experi- 
ment and  its  results.  Moreover,  sometimes  it  happens 
that  the  bitten  or  inoculated  animal  does  not  die,  and 
everything  has  to  be  done  over  again.  Finally,  as  a 
last  obstacle,  numerous  attempts  carried  on  for  a  long 
time  in  the  laboratory  of  Pasteur,  and  elsewhere,  had 
shown  that  it  was  impossible  to  discover  in  the  saliva 
of  rabid  animals  any  organism  having  an  assured  etio- 
logical relation  to  the  disease.  Pasteur,  after  having 
believed  that  he  had  discovered  it,  had  renounced  this 
idea,  which  he  had  had  the  prudence  not  to  publish, 
so  that  he  attacked  the  question  without  knowing 
whether  the  disease  was  a  virus  disease,  without  knowing 
or  being  able  to  cultivate  the  microbe,  and  even  without 
having  a  certain  and  quick  method  of  inoculation.  It 
is  here  that  we  shall  soon  see  the  power  of  the  experi- 
mental method  when  it  is  handled  at  the  same  time 
with  prudence  and  audacity.  It  is  a  marvelous  tool, 
having  an  extraordinary  power  of  penetration,  being 
able,  provided  it  is  handled  by  one  who  thoroughly 
understands  it,  to  work  even  in  obscurity,  like  those 
drills  which  attack  and  pulverize  everything  that  is 
presented  to  them  in  the  depths  of  a  black  pit,  provided 
that  they  are  entirely  in  the  grasp  of  the  man  who  di- 
rects them. 

The  general  symptoms  of  rabies  bore  witness  that  it  was 
especially  the  nerve  centers  which  were  attacked.  Dr. 
Duboué,  of  Pau,  had  already  observed  this  and  concluded 
that  not  simply  the  saliva  of  a  mad  animal  but  also  its 
nerve-substance  should  be  virulent.  Experiment  has 
demonstrated  the  j  ustice  of  this  conclusion.     Nerve  tissue, 


296  pasteur:  the  history  of  a  mind 

inserted  under  the  skin  of  an  animal,  can  give  it  rabies. 
But  this  method  of  transmission  is  quite  as  uncertain  and 
capricious  as  transmission  through  the  saliva.  Rabies 
does  not  always  appear,  and  it  sometimes  does  so  only  after 
a  prolonged  incubation  of  months.  Inoculation  under 
the  skin,  therefore,  is  an  uncertain  method.  But,  said 
some  one  in  the  laboratory  of  Pasteur,  why  not  try  to 
deposit  the  virus  in  the  nerve  centers,  since  it  is  there 
that  it  grows  and  reproduces  itself. 

For  that  purpose  it  was  not  necessary  to  know  the 
microbe,  nor  even  to  be  sure  that  there  was  one;  the  proof 
of  its  presence  and  its  development  would  not  be  micro- 
scopical examination,  but  the  appearance  of  rabies  in 
the  animal  inoculated.  As  a  culture  medium  the  nerve 
tissue  offers,  moreover,  guarantees  which  one  does  not 
find  either  in  the  saliva  or  even  in  the  blood,  both  of 
which  are  much  more  accessible  to  contamination  from 
the  exterior.  Furthermore,  it  seemed  to  be  a  chosen 
medium  for  the  virus  of  rabies,  and  to  fulfil  naturally 
for  it  that  condition  which  was  the  foundation  of  the 
culture  method,  and  which  was  realized  only  after  much 
labor  in  the  artificial  culture  media  for  the  anthrax 
bacteridium  and  the  microbe  of  chicken  cholera.  The 
main  thing  was  to  gain  access  to  it  properly  and  to  make 
an  antiseptic  inoculation  there.  The  surest  way  was 
to  attempt  to  inoculate  a  dog  under  the  dura  mater, 
by  trepanning.  "  Ordinarily  an  experiment  once  con- 
ceived and  talked  over  was  put  under  way  without  delay," 
says  Dr.  Roux.  "This  one,  on  which  we  were  counting 
so  much,  was  not  begun  immediately.  Pasteur,  who 
had  been  obliged  to  sacrifice  so  many  animals  in  the 
course  of  his  beneficent  studies,  felt  a  veritable  repug- 
nance toward  vivisection.  He  was  present  without 
too  much  squeamishness  at  simple  operations,  such  as 
a  subcutaneous  inoculation,  and  yet,  if  the  animal  cried 


STUDIES   ON   RABIES  297 

a  little,  Pasteur  immediately  felt  pity  and  lavished  on 
the  victim  consolation  and  encouragement  which  would 
have  been  comical  if  it  had  not  been  touching.  The 
thought  that  the  skull  of  a  dog  was  to  be  perforated 
was  disagreeable  to  him;  he  desired  intensely  that  the 
experiment  should  be  made,  but  he  dreaded  to  see  it 
Undertaken.  I  performed  it  one  day  in  his  absence; 
the  next  day,  when  I  told  him  that  the  intracranial 
inoculation  presented  no  difficulty,  he  was  moved  with 
pity  for  the  dog  :  '  Poor  beast  !  His  brain  is  without  doubt 
wounded.  He  must  be  paralyzed.'  Without  replying, 
I  went  below  to  look  for  the  animal  and  had  him  brought 
into  the  laboratory.  Pasteur  did  not  love  dogs;  but 
when  he  saw  this  one  full  of  life,  ferreting  curiously 
about  everywhere,  he  showed  the  greatest  satisfaction 
and  straightway  lavished  upon  him  the  kindest 
words.  He  felt  an  infinite  liking  for  this  dog  which 
had  so  well  endured  trepanning,  and  thus  had  put 
to  flight  for  the  future  all  his  scruples  against  it."1 

The  method  was  in  reality  discovered.  It  was  that 
of  making  pure  cultures  in  the  organism.  The  dog 
thus  trepanned  developed  rabies  in  fourteen  days, 
and  all  the  dogs  treated  in  the  same  fashion  behaved 
similarly.  It  was  now  possible  to  make  progress,  and 
from  that  moment  everything  went  on  as  in  the  case 
of  chicken  cholera  and  of  anthrax.2 

For  these  latter  maladies  the  virulence  can  be  varied 
by  changing  the  culture  medium.  Pasteur  had  likewise 
discovered,  for  chicken  cholera  as  well  as  for  anthrax, 
that  the  virulence  varied  with  the  transfer  of  the  microbe 
from  one  animal  species  to  another,  and  we  shall  soon 

1 L  Œuvre  médicale  de  Pasteur,  par  M.  le  Dr.  Roux,  Agenda  du  chim- 
iste, 1895. 

*  All  the  studies  on  rabies  are  summarized  in  Comptes  rendus  de  l' Acad- 
émie des  Sciences,  beginning  with  1881.  They  were  done  in  collaboration 
with  MM.  Chamberland,  Roux  et  Thuillier. 


298  pasteur:  the  history  of  a  mind 

re-survey  these  results  and  the  conclusions  which  can  be 
drawn  from  them.  In  the  case  of  rabies,  where  cultures 
could  be  made  only  on  the  living  creature,  this  method 
was  obligatory.  He  tried,  therefore,  the  inoculation 
of  a  rabbit  by  trepanning  and  saw  that  the  virus,  when 
thus  passed  from  rabbit  to  rabbit,  was  strengthened, 
and  that  the  duration  of  the  incubation  in  the  end  was 
no  more  than  six  days.  In  the  monkey,  on  the  contrary, 
the  virus  becomes  attenuated.  This  confirmed  the 
analogies  between  rabies  and  the  virus  diseases. 

But  if  the  spinal  cord  of  an  animal  that  has  died  of 
rabies  can  be  considered  as  a  pure  culture  of  the  virus, 
why  not  try  to  attenuate  the  virus  by  allowing  a  portion 
of  this  cord  to  become  old  in  contact  with  pure  air,  as  the 
virus  of  anthrax  is  attenuated  by  exposing  a  pure  culture 
to  pure  air.  Thus  occurred  wholly  naturally  this  great 
discovery  that  the  spinal  cord  from  a  rabid  animal, 
exposed  to  the  action  of  air,  in  an  atmosphere  free  from 
humidity,  loses  its  activity  on  drying.  After  14  days, 
the  virus  is  harmless  in  the  strongest  doses;  between  the 
fresh  cord  and  that  14  days  old,  there  is  a  whole  series  of 
degrees  of  attenuation.  "A  dog  that  receives  this 
rabic  spinal  cord  14  days  old,  then  the  following  day 
that  13  days  old,  then  that  12  days  old,  and  so  on  until 
the  fresh  cord  is  used,  does  not  contract  rabies  and  has 
become  immune  to  it.  Inoculated  in  the  eye  or  the 
brain  with  the  strongest  virus,  it  remains  healthy.  It 
is,  therefore,  possible  in  15  days  to  give  to  an  animal 
immunity  against  rabies.  Now  men,  bitten  by  mad 
dogs,  ordinarily  do  not  contract  the  disease  until  a  month 
or  even  more  after  the  bite,  and  this  period  of  incuba- 
tion can  be  utilized  for  rendering  the  bitten  person 
immune. 

"Experiments  made  on  dogs  bitten  and  inoculated 
were  successful  beyond  all  hope.     One  recalls  how,  with 


THE    PROBLEM    OF    IMMUNITY  299 

the  aid  of  MM.  Vulpian  and  Grancher,  the  experi- 
ments were  extended  to  man.  To-day  almost  20,000 
persons  have  undergone  this  antirabic  treatment  and  the 
mortality  occurring  among  these  treated  persons  has 
been  less  than  5  per  thousand. 

"The  discovery  of  the  prophylaxis  for  rabies  aroused 
everywhere  great  enthusiasm.  It  increased  the  popu- 
larity of  Pasteur  more  than  all  his  former  works.  In 
return  for  such  a  benefaction,  the  great  public  desired 
to  manifest  its  gratitude  in  a  manner  worthy  of  itself 
and  of  the  man  it  wished  to  honor.  It  was  then  that 
the  subscription  was  started  which  has  made  possible 
the  founding  of  the  Pasteur  Institute."1 

Once  again  the  method  had  brought  forth  fruit.  We 
could  further  cite,  as  proof  of  its  value,  the  vaccination 
for  erysipelas  of  swine,  preeminent  among  the  workers 
on  which  was  the  regretted  Thuillier.  But  we  should 
find  therein  only  what  we  already  know.  We  are  not 
writing  the  history  of  the  work  of  Pasteur,  but  that  of 
his  mind,  and  it  is  better  to  take  up  an  aspect  of  the 
question  of  viruses  which  we  have  not  yet  considered. 


VI 

THE  PROBLEM  OF  IMMUNITY 

The  theoretical  importance  of  all  these  facts  was 
superior  even  to  their  practical  importance.  This 
method  of  the  physiological  study  of  microbes  in  pure 
cultures  which  had  at  first  given  the  etiology  of  the 
different  diseases  studied,  which  later  had  furnished 
all  the  ideas  which  we  have  just  summed  up  on  varia- 
tions in  virulence,  was  about  to  exhibit  a  new  fecundity 
by  opening  up   the  problem  of  immunity,   on  which 

1  Roux,  1.  c,  p.  543. 


300  pasteur:  the  history  of  a  mind 

scientists  are  still  working,  and  on  which  the  last  word 
has  not  been  said. 

On  what  depends  that  immunity  which  vaccinated 
animals  possess,  which  is  also  possessed  by  animals  nat- 
urally resistant  to  certain  diseases  fatal  to  other  species? 
Why  does  the  cow  contract  anthrax  less  easily  than  the 
sheep  of  Beauce,  and  the  sheep  of  Algiers  less  easily 
still  than  the  cow?  Why  is  man  not  attacked  by  certain 
diseases  of  the  domestic  animals,  and  inversely?  Here 
were  questions  which,  yesterday  premature  and  auda- 
cious, could  now  be  stated  and  become  the  object  of  an 
experimental  study.  In  a  word,  it  was  not  alone  the 
mechanism  of  the  disease  which  ought  to  be  the  subject 
matter  for  experiment,  but  also  the  mechanism  of  health, 
that  is  to  say,  the  entire  physiology  of  the  living  creature, 
and  already  one  could  foresee  that  Pasteur  and  Claude 
Bernard  were  about  to  join  hands  to  contribute  to  a 
deeper  conception  of  the  life  of  the  cell. 

The  new  idea  which  Pasteur  brought  into  this  study 
was  the  idea  of  strife  between  two  cells  or  two  groups 
of  cells,  and  here  I  seem  to  be  advancing  a  daring  prop- 
osition, to  such  a  degree  does  the  idea  of  strife  form  a 
part  of  the  old  conception  of  disease  and  even,  gener- 
ally, of  the  appearance  of  the  sick  person.  During  the 
metaphysical  period  of  pathology,  when  the  direction 
of  life  was  attributed  to  a  vital  force  superposed  on  all 
the  organs,  one  had  been  led  to  imagine  the  disease  as 
a  distinct  entity,  entering  into  combat  with  the  vital 
force  in  the  organism.1  When,  through  the  progress 
of  physiology,  the  vital  force  was,  so  to  speak,  reduced 
to  an  infinite  number  of  cellular  lives,  each  having  its 

1  This  is  the  theory  of  homeopathy.  If  the  proper  drug  is  administered, 
that  is,  one  having  a  greater  affinity  for  the  entity  of  the  disease  than  the 
latter  has  for  the  body,  then  the  drug-spirit  and  the  disease-spirit  will 
combine  and  the  patient  will  return  to  his  normal  condition.  Vide 
Hempel's  Materia  Medica.     Trs. 


THE    PROBLEM   OF   IMMUNITY 


301 


modality  and  its  direction,  it  was  necessary  that  the 
idea  of  disease  also  be  changed,  and  we  have  already 
seen  the  efforts  made  to  ascribe  physico-chemical  origins 
to  pathology.  In  this  conception  the  old  idea  of  strife 
had  entirely  disappeared,  and  although,  for  Virchow, 
a  tumor  was  a  physiological  development  misplaced  in 
time  and  space,  that  is  to  say,  produced  where  it  ought  not 
be,  and  at  a  time  which  was  not  its  own,  it  was  difficult 
to  see  therein  anything  which  resembled  the  conception 
that  made  the  disease  something  at  war  with  the  vital 

force. 

It  is  for  this  reason  that  the  physiologists  were  so 
opposed  to  the  microbian  doctrines.  The  microbe, 
producing  a  chemical  phenomenon  or  causing  a  disease, 
was  the  sudden  reappearance  of  the  vital  force  in  regions 
from  which  it  was  desired  to  eliminate  it.  The  idea  of 
the  microbe  brought  back  in  the  clearest  manner  the 
idea  of  conflict,  of  strife  for  the  necessities  of  life,  of  the 
struggle  for  existence.  Such  is  the  idea  which  Pasteur, 
more  than  any  one  else,  was  instrumental  in  introduc- 
ing into  science  and  into  pathology. 

This  idea  in  its  turn  underwent  some  transformations 
in  his  mind.  At  the  time  of  the  publication  of  his 
Études  sur  la  maladie  des  vers  à  soie,  the  microbe  was  for 
him  a  pathogenic  cause  external  to  the  organism,  func- 
tioning simply  and  in  some  measure  irresistably.  In 
order  to  be  rid  of  the  disease,  the  parasite  must  be  dis- 
posed of.  This  is  what  Pasteur  had  done  for  the  corpus- 
cle of  the  pébrine.  It  was  what  had  been  done  before 
him  for  the  muscardine  fungus  and  the  itch  mite. 

This  rather  absurd  conception  of  bacterial  diseases 
was  for  Pasteur  in  perfect  accord  with  what  he  then  knew 
of  microbes.  He  believed  that  the  bacterial  species 
were  nearly  constant  in  form  and  possessed  immutable 
properties.     Transferred  from  medium  to  medium  they 


302  pasteur:  the  history  of' a  mind 

would  always  cause  the  same  reaction,  which  was  a 
surer  means  of  recognition  than  their  microscopical 
appearance.  Transferred  in  the  same  way  to  a  living 
creature  they  would  produce  a  definite  disease,  that  is, 
one  which  was  always  the  same  when  the  avenue  of 
entrance  was  the  same,  and  which  became  thereby  a  sort 
of  morbid  entity:  thus  bringing  us  back,  in  the  experi- 
mental field,  to  the  oldest  conceptions  of  medicine. 
Studies  on  the  flacherie  scarcely  modified  this  point 
of  view.  They  had  shown  merely  that  the  microbe, 
in  order  to  become  active,  sometimes  needed  to  be  aided 
by  external  conditions.  But  when  it  did  act,  it  always 
produced  the  same  results. 

In  short,  when  nearly  60  years  of  age,  Pasteur  dis- 
covers facts  which  are  not  in  accord  with  this  old  concep- 
tion. These  relate  to  the  attenuation  of  virus.  One 
and  the  same  microbial  species  can  invest  itself,  accord- 
ing to  the  culture  conditions,  with  characters  which 
render  it  unrecognizable  to  one  who  has  not  followed 
it  closely  through  all  of  its  transitions.  I  have  stated 
above  how  Pasteur  had  endeavored  to  convince  himself 
that  there  were  in  his  cultures  of  the  septic  vibrio  two 
species  of  unequal  virulence,  which  the  culture  conditions 
enabled  him  to  separate.  He  refused  to  admit  that  these 
culture  conditions  could  produce  them.  The  same  may 
be  said  of  the  chicken  cholera.  It  was  the  struggle  be- 
tween the  old  spirit  and  the  new,  and  one  must  admire 
the  readiness  with  which  Pasteur  abandoned  his  first 
conceptions  when  experiment  had  taught  him  that  they 
were  not  in  accord  with  the  facts. 

It  was  with  ardor  and  without  regret  that  he  threw 
himself  into  this  new  path,  divining  the  resources  which 
he  would  find  there  for  attacking  the  greatest  and  most 
delicate  problems  of  pathology.  He  could  henceforth 
take  up  again  his  old  idea  of  conflict,  no  longer  that 


THE    PROBLEM    OF    IMMUNITY  303 

brutal  strife  where  the  only  possible  means  of  interven- 
tion consisted  in  the  suppression  of  one  of  the  adversaries, 
but  a  gentle  strife  which  one  might  attempt  to  direct  by 
augmenting  or  diminishing  the  forces  of  one  of  the  con- 
testants. It  was  only  a  question  of  finding  the  ground 
and  the  object  of  the  strife,  and,  for  that  purpose,  he  had 
the  experimental  method:  it  was  possible,  working  with 
a  single  species  subject  to  anthrax,  to  study  bacteridia 
of  different  degrees  of  virulence;  it  was  possible,  with 
the  same  bacteridium,  to  study  different  species,  or 
animals  of  the  same  species  unequally  vaccinated,  which 
made  them,  to  a  certain  degree,  different  animals.  We 
see  what  a  field  of  labor  opened  before  him.  It  is 
characteristic  of  certain  discoveries  that  they  suddenly 
reveal  vast  horizons.  Pasteur  had  climbed  little  by 
little  to  one  of  those  mountain  heights  from  which 
a  whole  new  country  is  visible.  He  plunges  into 
it  with  delight.  Let  us  accompany  him.  We  can 
no  longer,  follow  him  closely  and  must  abandon  the  his- 
torical order.  In  the  first  place,  we  have  reached  the 
latter  part  of  his  life  and  his  later  conceptions.  In  the 
second  place,  what  interests  us  is  the  plan  of  the  edifice, 
and  not  the  order  in  which  its  different  parts  have  been 
erected.  If  we  wish  to  know  which  part  belongs  to 
Pasteur  himself,  which  part  he  has  built,  we  must  take 
it  in  the  condition  in  which  Pasteur  left  it,  with  its 
finished  parts,  with  its  stones  yet  unplaced,  and  with  a 
brief  indication  of  what  the  progress  of  science  has 
contributed  to  it. 


304  pasteur:  the  history  of  a  mind 

VII 
VIRULENCE  AND  ATTENUATION 

Attenuation  is  a  general  phenomenon.  After  having 
determined  its  occurrence  in  chicken  cholera,  the 
anthrax  bacteridium,  rabies,  and  the  organism  of 
erysipelas  of  the  pig, l  Pasteur  found  it  in  a  microbe  occur- 
ring in  horses  which  had  died  from  typhoid  fever,  and 
in  another  organism  derived  from  the  saliva  of  a  child 
attacked  by  hydrophobia,  which  last  mentioned  or- 
ganism was  found  later  to  be  the  pneumococcus  of 
Talamon-Fraenkel.  All  these  bacilli  became  attenuated 
when  they  were  allowed  to  grow  old  in  the  fluid  culture 
medium. 

But  what  do  we  mean  by  this  expression  "grow  old?" 
Age  is  a  result,  and  cannot  be  an  active  cause.  It  ac- 
companies attenuation,  it  does  not  produce  it;  or,  rather, 
the  same  cause  which  produces  one,  at  the  same  time 
produces  the  other.  When  we  search  for  some  physico- 
chemical  influence  which  might  come  into  play,  we  think 
at  once  of  oxygen. 

The  micrococcus  of  chicken  cholera  is,  for  example, 
an  aerobe  in  the  culture  flask  and  in  the  organism. 
When  it  ceases  to  multiply  in  the  culture  medium,  it 
continues  to  respire  there,  to  give  off  carbonic  acid 
by  consuming  its  own  tissues.  It  contracts  and  shrinks 
visibly  (Fig.  22).  Its  attenuation,  which  is  a  proof  of 
its  debility,  is  probably  due  to  this  internal  process,  and 
in  reality  experiment  teaches  that  when  the  supply  of 
oxygen  is  limited  by  sealing  the  tubes,  allowing  only  a 
small  amount  of  this  gas  to  be  present,  the  virulence  is 
maintained  much  longer.  It  is  the  same  in  all  cases, 
and  always  the  oxygen,  regarded  as  the  agent  of  com- 

1Fr.  Rouget  de  porc;    Ger.  Schweinerothlauf.     Trs. 


VIRULENCE   AND   ATTENUATION  305 

bustion  of  the  tissues  in  the  absence  of  food,  and  conse- 
quently as  the  agent  of  enervation,  is,  at  the  same  time, 
an  agent  of  attenuation.  Attenuation  and  weakening 
are  synonymous,  and  we  have  here  a  conception  which 
harmonizes  well  with  our  idea  of  strife  in  the  microbial 
diseases.  That  which  is  harmful  to  the  microbe  is  of 
value  to  its  host. 

We  are  then  justified  in  asking  ourselves  if  all  these 
causes  of  weakening  on  the  part  of  the  microbe,  all  these 
factors  which  contribute  more  or  less  quickly  to  its 
death,  do  not  first  cause  it  to  pass  through  a  series  of  suc- 
cessive attenuations,  that  is,  transform  it  into  vaccines. 
To  this  new  question,  experiment  replies  without  hesi- 
tation, "Yes."  In  a  general  way,  attenuation  is  one  of 
the  forms  of  the  gradual  weakening  of  a  microbial  cell 
which  is  on  its  way  to  death,  and  every  action  harmful 
to  the  microbe  begins  by  diminishing  its  virulence. 
Such,  for  example,  is  heat,  too  high  a  degree  of  which 
kills  the  microbe,  as  we  know.  Between  the  optimum 
temperature  for  culture  and  the  death  point  exists  a 
zone  of  attenuation,  observed  by  M.  Toussaint  and 
carefully  studied  by  M.  Chauveau,  for  the  anthrax 
bacteridium.  The  duration  of  the  heating  should  be  in 
inverse  ratio  to  the  elevation  of  the  temperature  and,  for 
a  given  temperature,  directly  proportional  to  the  degree 
of  attenuation  to  be  obtained. 

Next  to  the  action  of  heat  naturally  comes  that  of  the 
light  of  the  sun.  It  kills  the  microbe  after  a  certain 
length  of  exposure  to  it,  but  before  killing,  it  causes 
attenuation.  This  is  the  conclusion  from  my  experi- 
ments, followed  by  those  of  M.  Arloing. 

So    much   for    the    physical    agents.     Now    for    the 

chemical  ones.     Oxygen  is  a    physiological    factor    of 

the  greatest  importance,  and  we  have  already  examined 

its  rôle  in  this  relation.     But  it  plays  also  a  rôle  more 

20 


306  pasteur:  the  history  of  a  mind 

exclusively  chemical,  a  toxic  rôle,  demonstrated  by 
P.  Bert.  All  microbes  require  a  small  amount  of  oxygen 
and  are  injured  by  an  excess  of  it.  The  anaerobes  must 
have  traces  of  it  but  die  in  ordinary  air.  The  aerobes 
live  in  ordinary  air  but  die  in  compressed  oxygen. 
Between  the  physiological  limits  and  the  toxic  limits 
there  is,  moreover,  a  zone  of  attenuation,  studied  by  M. 
Chauveau  for  the  anthrax  bacteridium. 

After  oxygen,  come  naturally  the  antiseptics  which, 
likewise,  when  present  in  very  small  proportions,  are. 
harmless  or  even  beneficial  to  the  microbes,  but  if 
present  in  larger  quantities  kill  them.  MM.  Chamber- 
land  and  Roux  have  studied  the  action  of  phenic  acid, 
of  bichromate  of  potash  and  of  sulphuric  acid  on  the 
anthrax  bacteridium  and  have  discovered  in  this  way 
some  curious  facts  to  which  we  shall  soon  return. 

In  short,  there  are  several  means  of  producing  from  the 
same  virulent  race  a  whole  series  of  races  more  and  more 
attentuated.  Up  to  this  time  we  have  studied  them  only 
as  vaccines.  In  order  fully  to  investigate  their  rôle  from 
this  new  point  of  view,  it  is  necessary  to  study  them  in 
themselves. 

How  do  bacteridia  which  are  not  equally  attenuated 
differ  physiologically?  They  are  very  much  alike  in 
bouillon  cultures.  When  attenuated  they  produce  rods 
which  separate  easily  and  diffuse  through  the  culture 
medium,  clouding  it,  while  the  virulent  bacteridia 
adhere  in  flakes,  which  float  in  the  midst  of  a  clear  liquid. 
But  their  physiological  needs  are  the  same,  and  it  is 
almost  impossible  to  differentiate  them  by  means  of  the 
microscope.  For  that  purpose  they  must  be  inoculated 
into  living  creatures. 

Let  us  study  them  in  animals.  In  proportion  as  the 
bacteridium  becomes  attenuated,  we  find  that  it  ceases, 
first,  to  become  virulent  for  cattle,  but  that  it  is  still 


VIRULENCE   AND   ATTENUATION  307 

capable,  at  this  time,  of  killing  sheep;  attenuated  a  little 
more  it  ceases  to  be  fatal  to  sheep,  but  still  kills  rabbits 
and  guinea-pigs.  When  it  no  longer  kills  adult  guinea- 
pigs,  it  still  kills  young  guinea-pigs  or  young  mice.  This 
is  also  true  for  other  microbes. 

Virulence  appears  to  us,  therefore,  to  be  an  intrinsic 
quality  of  which  the  microbe  will  be  divested  more  and 
more  until  it  becomes  harmless.  But  here  is  a  fact 
which  proves  that  things  are  not  as  simple  as  they  seem. 
If  virulence  were  only  this,  the  different  methods  of 
attenuation  would  destroy  it  in  the  same  fashion,  and 
the  order  in  which  the  different  species  of  animals  are 
attacked  would  be  always  the  same.  But  experiment 
shows  that  this  order  varies  according  to  the  method  of 
attenuation.  The  anthrax  bacteridium  attenuated,  for 
example,  with  bichromate  of  potash,  in  the  experiments 
of  MM.  Chamberland  and  Roux,  as  we  shall  see  at  once, 
may  still  kill  the  sheep  or  at  least  make  them  very  ill, 
leaving  them  in  the  latter  case  vaccinated,  while  it 
produces  no  effect  whatever  on  rabbits  or  guinea-pigs, 
and  does  not  even  vaccinate  them.  It  is  exactly  the 
reverse  of  the  behavior  of  the  anthrax  bacteridium 
attenuated  by  growth  at  42°  to  43°C,  which  kills  guinea- 
pigs  and  rabbits  at  a  stage  when  it  is  harmless  for  the 
sheep,  and  does  not  even  vaccinate  them.  We  obtain 
the  same  results  with  spores  of  the  anthrax  bacteridium 
attenuated  by  the  action  of  a  temperature  of  35°C,  in  a 
liquid  containing  2  per  cent  sulphuric  acid. 

Thus  virulence  is  not,  as  we  might  suppose,  an  absolute 
quality,  diminishing  little  by  little  after  the  fashion 
of  reserve  food;  it  is  a  relative  quality,  in  the  estimation 
of  which  not  only  conditions  pertaining  especially  to  the 
microbe  must  be  taken  into  account,  but  also  those 
pertaining  to  the  nature,  age,  and  as  we  shall  soon  see,  the 
individuality   of   the   animal   on   which   it   is   studied. 


308  pasteur:  the  history  of  a  mind 

According  to  our  way  of  looking  at  things,  nothing  is  less 
surprising.  The  word  " virulence"  sums  up  the  result 
of  the  conflict  between  two  organisms.  It  is  necessary, 
therefore,  to  take  into  account  the  qualities  of  the  two 
adversaries. 


VIII 
RETURN  TO  VIRULENCE 

We  shall  reach  the  same  conclusion  by  an  inverse 
method,  that  is,  by  examining  the  conditions  determin- 
ing the  return  of  virulence  in  a  microbe  which  has  lost  it. 
We  know  that  these  positive  and  negative  variations  of 
virulence  may  be  produced  by  simple  changes  in  the 
culture  medium,  but,  from  this  standpoint,  they  are  of 
little  interest.  These  variations  become  interesting  only 
as  they  manifest  themselves  in  living  creatures.  Let  us 
see,  therefore,  if  we  cannot  revive  virulence  by  passage 
through  different  species  of  animals  unequally  sensitive. 

We  have  obtained,  it  will  be  remembered,  a  strain  of 
the  anthrax  bacteridium  absolutely  harmless,  then  one 
very  much  weakened,  still  able  to  kill  guinea-pigs  a  day 
old,  but  not  to  kill  older  guinea-pigs  nor  other  species  of 
animals,  then,  starting  from  this  one,  a  whole  series  of 
microbes  more  and  more  virulent.  Can  one  bring  back 
the  most  attenuated  strains  to  a  state  of  the  highest 
virulence?  Experience  replies,  "No,"  in  the  case  of  a 
completely  non-virulent  anthrax  bacteridium,  for  it 
escapes  our  experimentation  by  refusing  to  grow  in  any 
living  organism;  it  is  henceforth  fixed,  and  if  it  ever 
returns  to  virulence,  it  will  be  by  passing  through  a  new 
species  of  animal  different  from  those  which  hitherto 
have  been  shown  to  be  capable  of  contracting  anthrax. 

But  the  case  is  different  for  those  strains  which  still 


RETURN   TO  VIRULENCE  309 

preserve  an  action  on  a  living  species.  Let  us  take  for 
example  the  most  attenuated,  that  which  is  barely  able 
to  kill  a  guinea-pig  a  day  old:  if  we  inoculate  its  blood 
into  a  guinea-pig  of  the  same  age,  that  of  the  second 
animal  into  a  third,  and  so  on,  we  shall  shortly  see  the 
virulence  of  the  bacteridium  return  little  by  little. 
Soon  we  shall  be  able  to  kill  with  it  guinea-pigs  three  or 
four  days  old,  a  week,  a  month  old,  and  finally  sheep. 
By  successive  cultures  in  living  media,  the  bacteridium 
has  been  restored  to  its  original  virulence. 

It  is  justifiable  to  form  out  of  these  facts  a  general  rule, 
in  accordance  with  our  theory.  A  microbe  introduced 
into  the  body  of  an  animal  is  not  living  under  the  same 
conditions  as  one  sown  in  an  inert  vessel;  it  is  subjected 
to  the  pressing  alternative  of  living  or  dying,  of  being 
victorious  or  vanquished.  Vanquished,  its  history  is 
soon  written;  victorious,  it  will  come  out  of  the  struggle 
strengthened,  that  is  to  say,  having  complied  with  the 
conditions  of  its  new  medium,  it  is  better  prepared  to 
accommodate  itself  therein  anew.  If  it  is  transferred 
several  times  from  individual  to  individual  of  the  same 
race,  without  having  been  influenced  by  external  con- 
ditions in  the  interim  between  two  passages,  we  may 
expect  to  see  its  virulence  augmented  and  in  some  degree 
fixed  for  the  race  and  for  the  customary  mode  of  trans- 
mission in  this  race.  Thus  the  bacteridium  of  sheep  an- 
thrax, for  example,  living  for  a  long  time  on  our  soil,  is 
acclimated  to  some  degree  in  the  race  which  shelters  it, 
and  its  virulence  varies  little  from  one  subject  to  another, 
and  from  one  year  to  another  for  the  same  country, 
The  same  thing  is  true,  to  a  certain  extent,  for  Jenner's 
vaccine,  if  it  is  transferred  directly  from  arm  to  arm  on 
unvaccinated  healthy  individuals,  and  if  it  is  carefully 
preserved  between  the  two  operations.  The  same  thing 
is  also  true  for  the  virus  of  rabies  administered  by  tre- 


310  pasteur:  the  history  of  a  mind 

panning,  after  a  certain  number  of  passages  through 
individuals  of  the  same  species. 

Having  once  attained  this  stability,  which  is  not  its 
maximum  virulence  for  the  race,  as  we  shall  see  later, 
the  virus  preserves  this  degree  of  virulence  practically 
unchanged,  if  the  paths  of  penetration  do  not  vary. 
This  increased  virulence  may  permit  it  to  invade  another 
race  or  another  species.  Thus  our  anthrax  bacteridium, 
invigorated  by  a  passage  through  the  guinea-pig,  can 
infect  the  sheep.  But  there  may  also  be  produced  cases 
analogous  to  those  in  the  experiments  of  MM.  Chamber- 
land  and  Roux,  in  which  the  virulence  augmented  for 
one  species  will  be  diminished  for  another,  or  inversely, 
and  we  reach  a  third  possible  case,  that  of  the  diminution 
of  virulence  for  one  species  by  passages  through  another 
species. 

We  shall  find  an  example  of  this  fact,  so  clear  that  it  is 
almost  diagrammatic,  in  the  work  of  Pasteur  and  Thuil- 
lier,  on  the  erysipelas  of  the  pig.  This  disease  is  due  to 
the  development  in  the  tissues  of  the  animal  of  a  very 
short  and  slender  rod.  It  goes  through  its  stages  of 
evolution  very  rapidly,  and  may  cause  death  in  some 
hours. 

It  is  not  confined  to  swine,  but  may  also  be  communi- 
cated to  the  pigeon  and  the  rabbit.  If  there  is  injected 
into  the  pectoral  muscles  of  a  pigeon  the  microbe  of  the 
erysipelas  taken  from  a  diseased  pig,  or  from  a  culture  in 
veal  bouillon,  the  pigeon  dies  in  from  6  to  8  days, 
after  having  shown  the  external  symptoms  and  the  som- 
nolence of  chicken  cholera.  We  might  believe  that  the 
two  diseases  are  identical  if  the  organism  of  the  erysipelas 
were  not  absolutely  harmless  to  the  chicken,  which  is  so 
sensitive  to  the  action  of  the  cholera  microbe. 

If  the  blood  of  the  first  pigeon  is  injected  into  a  second, 
the  blood  of  the  second  into  a  third,  and  so  on,  the  malady 


RETURN   TO  VIRULENCE  311 

becomes  acclimated  in  the  pigeon,  makes  it  sick  and 
somnolent  more  quickly,  kills  it  sooner,  and  the  blood 
of  the  last  pigeon  injected  into  the  pig,  manifests  there 
a  virulence  superior  to  that  of  the  most  infectious  mate- 
rial from  a  pig  which  has  died  of  erysipelas,  even  if  the 
pig  was  naturally  infected.  Here  we  have  then  aug- 
mentation of  virulence  for  the  pig  by  passing  the  or- 
ganism through  the  pigeon.  The  maximum  to  which  a 
virus  can  attain  by  passage  through  a  race  is,  therefore, 
not  always,  the  maximum  for  that  race. 

There  we  have  a  case  of  augmentation,  here  is  a  case  of 
attenuation  to  which  I  wish  especially  to  call  attention. 
Let  us  substitute  the  rabbit  for  the  pigeon  in  this  series 
of  experiments.  The  microbe  becomes  accustomed  to 
the  rabbit;  all  the  animals  die,  but  if  we  inoculate  pigs 
with  the  blood  of  the  last  rabbits  for  comparison  with 
that  taken  from  the  first  rabbits  in  the  series,  we  find  a 
progressive  diminution  of  virulence.  Soon  the  blood 
of  rabbits,  inoculated  into  pigs,  no  longer  kills  them; 
it  only  makes  them  sick  and  leaves  them  vaccinated 
against  the  fatal  erysipelas.  Entirely  parallel  facts 
have  been  worked  out  with  other  microbes.  They 
furnish  a  method  of  attenuation  of  viruses  by  passages 
through  living  species,  and  increase  our  means  of  action 
in  a  field  of  studies  the  future  of  which  will  show  its 
astonishing  fruitfulness.1 

We  have  now  come  back,  apparently,  to  a  conclusion 
already  stated  :  Virulence  is  a  state  of  perpetual  becoming. 
But  how  much  we  have  developed  this  idea,  and  what 
precision  the  new  facts  have  given  to  it,  and  to  the  bond 
of  theory  which  has  enabled  us  to  unite  them!     In  the 

1  This  prediction  has  been  more  than  fulfilled.  Since  this  book  was 
written  very  wonderful  advances  have  been  made  in  bacterio-therapy, 
the  most  striking  of  which  have  been  the  control  of  diphtheria  and  the 
prevention  of  typhoid  fever  and  of  tetanus.     Trs. 


312  pasteur:  the  history  of  a  mind 

beginning  we  ascribed  variations  in  virulence  to  the 
microbe  itself  and  there  was  there  a  vast  field  for  evolu- 
tions, but  it  did  not  embrace  all  the  possible  ones.  We 
have  been  obliged  to  add  to  it  those  which  come  from 
the  variation  of  the  living  organisms  in  which  the  mi- 
crobes establish  themselves,  and  the  virulence  which  we 
see  results  from  an  infinite  number  of  combinations  of 
these  two  causes  of  variation. 


IX 

CHEMICAL  AND  HUMORAL  THEORIES  OF 
IMMUNITY 

From  what  we  have  just  said  it  follows  that  the  word 
virulence  has  no  meaning  either  in  relation  to  the  microbe 
or  to  the  host.  It  signifies  little  more  than  the  relation 
between  strength  and  resistance,  without  telling  us 
anything  about  the  absolute  value  of  these  two  forces. 
A  microbe  which  does  not  kill  a  given  animal  or  does  not 
make  it  ill  is  devoid  of  virulence  with  respect  to  that 
animal,  and  one  might  believe  from  this  statement  that 
all  the  truths  which  we  have  discovered  are  naïvetés,  or 
mere  definitions  of  words;  that  would  be  making  a  great 
mistake.  What  we  have  discovered,  in  reality,  is  a  new 
field  of  study.  With  respect  to  this  or  that  animal,  such 
or  such  a  microbe  may  remain  harmless  for  many 
reasons.  It  cannot  develop  in  its  tissues,  or,  if  it  does 
develop,  deposits  there  no  injurious  substances,  or  even, 
perhaps,  produces  beneficial  effects,  leading  to  increased 
resistance.  The  field  of  hypotheses  is  unlimited.  Let 
us  see  what  experience  offers,  and  let  us  observe  how 
much  the  field  of  experiment  has  been  extended,  thanks 
to  Pasteur. 

Here  are  normal  sheep  inoculated,   some  with  the 


CHEMICAL  AND  HUMORAL  THEORIES  OF  IMMUNITY      313 

virulent  bacteridium,  others  with  the  attenuated  bacteri- 
dium.  The  first  develops  and  kills  the  sheep.  The 
second,  after  a  period  of  growth  made  with  more  or  less 
difficulty  and  causing  a  transitory  illness  of  the  sheep, 
abandons  the  struggle  and  leaves  the  animal  more  or 
less  vaccinated.  This  is  one  method  of  studying  the 
influence  of  the  bacteridium  alone. 

Now  elt  us  take  a  normal  sheep  and  a  vaccinated 
sheep,  into  which  we  inoculate  a  very  virulent  strain  of 
the  anthrax  bacteridium.  It  kills  the  first  and  has  no 
effect  on  the  second.  Here  we  have  a  way  to  study  the 
influence  of  immunity  acquired  by  a  former  vaccination. 

Let  us  take  now  a  French  sheep  and  an  Algerian  sheep  ; 
let  us  inoculate  both  of  them  with  a  light  dose  of  a  viru- 
lent strain  of  the  bacteridium.  The  first  will  die,  the 
second  will  resist,  after  an  illness  in  general  benign.  In 
this  we  have  the  influence  of  race  or  of  natural  immunity. 

The  French  sheep  has  a  natural  immunity  for  the 
attenuated  bacteridium;  the  Algerian  sheep,  a  natural 
immunity  against  the  virulent  disease;  the  vaccinated 
sheep  an  acquired  immunity,  more  or  less  marked;  the 
dog,  a  natural  and  absolute  immunity.  In  all  the  cases, 
the  natural  or  acquired  immunity,  when  it  is  complete,  is 
correlative  with  the  non-development  of  the  bacteridium, 
which  instead  of  invading  the  tissues,  remains  confined 
to  the  point  of  inoculation  or  its  vicinity,  and  finally 
perishes  there. 

What  is  the  cause  of  this  non-development  of  a 
living  cell  which  has  been  sown?  This  question  is  what 
the  inquiry  led  to  !  We  see  that  it  was  precise.  It  was 
already  a  conquest  only  to  be  able  to  state  it  thus.  Until 
that  time  it  had  been  necessary  to  bow  down  without 
seeking  to  penetrate  the  mystery.  What  reply,  in  fact, 
can  be  given  to  this  general  question  :  Why  is  the  sheep 
sensitive  to  anthrax,  and  the  dog  not  sensitive?     Why 


314  pasteur:  the  history  of  a  mind 

is  man  alone  able  to  contract  syphilis?1  These  are 
questions  which  one  did  not  even  dream  of  putting  to 
himself.  But  after  living  viruses  were  discovered  and 
their  conditions  of  growth  were  known,  man  could  ask 
himself  why  they  develop  here  and  not  there,  on  the 
French  sheep  and  not  on  the  Algerian  sheep,  both  of 
which  are,  however,  authentic  sheep. 

For  an  answer  to  this  embarrassing  question,  Pasteur 
sought  quite  naturally,  as  any  man  of  science  would  do, 
in  his  experience  and  memory.  They  were,  it  is  true,  the 
experience  and  the  memory  of  a  chemist,  and  the  question 
did  not  remain  long  in  the  field  where  he  first  placed  it. 
But  all  theory  is  good  which  foresees  new  facts,  and 
however  inexact  it  appears  to-day,  the  explanation  of 
Pasteur  has  had  that  merit. 

He  knew,  through  his  long  experience  with  fermenta- 
tions, that  even  when  one  works  in  vitro  the  smallest  cir- 
cumstances suffice  to  permit  or  to  hinder  the  development 
of  a  microbe.  When  he  saw  certain  of  them  demand  veal- 
bouillon  and  certain  others  fowl-bouillon,  it  did  not  sur- 
prise him  that  a  particular  disease  was  peculiar  to  a 
particular  species,  and  another  disease  to  another  species. 
Neither  was  it  astonishing,  knowing  how  hard  to  please 
the  microbes  are  on  questions  of  temperature,  that  the 
chilled  fowl  should  contract  anthrax,  while  at  its  ordinary 
temperature  it  remained  unaffected.  Finally,  knowing, 
as  we  have  said,  that  the  chicken  cholera  microbe  refuses 
to  develop  again  in  a  medium  in  which  it  has  already 
lived,  why  be  astonished  that  it  should  refuse  to  live 
again  in  an  organism  which  it  has  already  invaded? 
There  was,   in  these  exclusively  physical  or  chemical 

1  We  now  know  from  the  studies  of  Metchnikoff  that  syphilis  is  in- 
oculable into  apes,  and  from  those  of  Noguchi  into  rabbits  the  living 
testicles  of  which'  are  the  best  culture  medium  for  the  propagation  of  the 
Treponema  pallidum — the  protozoan  cause  of  syphilis.     Trs. 


CHEMICAL  AND  HUMORAL  THEORIES  OF  IMMUNITY      315 

facts,  a  wholly  natural  explanation  of  the  non-recurrence 
of  virus  diseases. 

Let  us  investigate  in  this  direction.  Why  does  not  the 
same  bouillon  culture  nourish  easily  a  second  time  the 
species  which  has  already  lived  in  it  ?  The  failure  might 
result  from  one  of  two  things:  either  the  organism 
removed  from  the  bouillon  the  first  time  a  substance 
needed  in  its  development,  or  else  it  deposited  in  it  an 
injurious  substance. 

Pasteur  and  his  colleagues  inclined  toward  the  first  ex- 
planation. M.  Chauveau,  on  the  contrary,  favored  the 
second  and  supported  it  on  two  arguments  of  unequal 
value.  He  was  of  the  opinion,  for  instance,  that  the 
vaccination  of  the  fœtus  by  the  mother,  that  is  to  say, 
the  transmission  of  immunity  through  the  placenta, 
which  he  had  often  had  occasion  to  verify  in  anthrax,  and 
which  MM.  Arloing,  Cornevin  and  Thomas  had  just 
proved  for  the  symptomatic  anthrax,  was  better  ex- 
plained by  the  introduction  of  an  injurious  substance 
into  the  blood  of  the  foetus,  than  by  the  disappearance  of 
a  needed  substance.  The  two  bloods  of  the  mother  and 
of  the  foetus  being  constantly  in  position  to  exchange 
chemical  substances,  are  likewise  in  position  to  lose  or 
to  acquire,  and  there  appear  to  be  no  reasons  for  be- 
lieving that  preference  is  given  one  over  the  other. 
Another  argument  of  M.  Chauveau  was  worth  more. 
He  called  attention  to  the  curious  influence  of  the  quan- 
tity of  virus  used  in  inoculation.  The  Algerian  sheep  is 
immune  to  doses  which  kill  the  French  sheep,  but,  if 
we  increase  the  dose,  we  also  kill  the  Algerian  sheep. 
If  it  is  much  diminished,  the  French  sheep  resists  in  its 
turn,  experiencing  only  an  illness,  from  which  it  emerges 
vaccinated.  This  is  not  explained  by  the  hypothesis  of 
Pasteur.  If  there  is  lacking  in  the  sheep  an  element 
needful  for  the  multiplication  of  the  bacteridium,  we 


316  pasteur:  the  history  op  a  mind 

do  not  understand  why  its  absence  no  longer  interferes 
with  growth  when  the  number  of  microbes  increase 
which  have  need  of  it  for  their  development.  On  the 
contrary,  it  is  much  more  comprehensible  why  the 
presence  of  an  injurious  substance  can  stop  a  small 
detachment  of  the  enemy,  and  not  a  large  troop. 

It  is  useless  to  dwell  upon  the  discussion  of  these  ex- 
planations of  immunity,  both  of  which  may  indeed  have 
their  part  in  the  phenomenon,  but  cannot  play  a  stellar 
rôle.  Strictly  speaking,  they  are  sufficient  to  explain 
the  immunity  produced  by  vaccination,  but  they  weaken 
when  it  is  a  question  of  explaining  the  duration  of  immu- 
nity. How  can  we  admit  the  persistence  for  years  of 
this  injurious  element,  or  the  absence  of  the  necessary 
element,  when  nutrition  and  destructive  metabo- 
lism bring  and  remove  such  varied  elements.  The 
element  duration  is  represented  in  the  tissues,  not  by 
the  chemical  substances  which  compose  them,  but  by 
their  permanent  form — by  the  cell. 

The  two  explanations  which  we  have  just  considered 
are  not  the  only  ones  which  have  been  proposed.  There 
have  been  successively  attributed  to  the  humors,  and 
to  the  liquids  of  the  animal  economy,  a  destructive 
power  for  microbes,  an  attenuating  power,  an  anti- 
toxic power,  all  these  powers  depending  solely  on  con- 
ditions of  the  physico-chemical  order.  Without  entering 
into  a  detail  which  however  important  it  is,  would  be 
out  of  place  here,  it  can  be  said  that  all  these  theories 
have  shown  themselves  to  be  powerless  to  explain  the 
great  fact  of  the  creation  and  the  persistence  of  immunity. 
As  to  the  creation  of  this  property  in  the  individual, 
either  it  has  been  found  that  the  liquids  in  circulation 
or  the  humors  that  occur  in  the  interior  of  the  body, 
did  not  have  the  destructive,  attenuating,  or  antitoxic 
power  which  we  find  in  them  outside  of  the  organism, 


CELLULAR   THEORY   OF   IMMUNITY  317 

or  else  if  they  did  have  these  powers,  they  were  without 
apparent  relation  to  the  resistant  or  vaccinated  state 
of  the  animal.  For  the  conservation  of  immunity,  the 
same  criticisms  apply  as  to  the  theories  of  Pasteur  and 
Chauveau.  A  chemical  action,  whatever  it  may  be, 
cannot  be  lasting  in  an  organism  in  which  all  the  chemi- 
cal elements  are  constantly  being  renewed.  There  is 
only  the  cell  which  lasts,  because  it  lives.  It  is  more 
likely  that  the  explanation  of  immunity  lies  in  the 
cellular  theories  than  in  the  humoral  theories  which  we 
have  just  briefly  reviewed. 


X 

CELLULAR  THEORY  OF  IMMUNITY 

Pasteur,  who  in  his  heart  was  indifferent  to  theories 
and  asked  of  them  only  that  they  suggest  experiments 
to  him,  held  for  a  long  time  a  purely  cellular  conception 
of  microbial  disease.  It  was  by  a  struggle  between  the 
red  blood  corpuscles  and  the  bacteridium  that  he  ex- 
plained in  1878  the  resistance  of  the  living  fowl  to  anthrax, 
and  we  see  him  at  every  instant,  in  that  period,  having 
recourse  to  vital  resistance,  and  saying:  " Among  the 
lower  forms  of  life,  still  more  than  in  the  higher  species 
of  plants  and  animals,  life  prevents  life."  Again,  it  was 
this  same  sentiment  which  guided  him  in  the  experiments 
which  we  have  seen  him  making,  to  prevent  the  develop- 
ment of  the  anthrax  bacteridium  by  inoculating  at  the 
same  time  with  some  common  bacteria.  Pasteur,  how- 
ever, was  conscious  of  not  having  laid  hold  of  the  vital 
point  of  the  mechanism  of  the  resistance  of  the  organism, 
and  it  is  perhaps  for  that  reason  that  when  he  heard  of 
the  researches  of  Metchnikoff  on  phagocytosis,  he  gave 


318  pasteur:  the  history  of  a  mind 

immediate  attention  to  them.  It  is  his  letter,  inserted 
in  the  first  number  of  the  Annales  de  l'Institut  Pasteur, 
which  first  pointed  out  to  the  French  public  the  re- 
searches of  M.  Metchnikoff. 

The  simplicity  of  this  conception  was  striking.  These 
white  corpuscles  of  the  blood  and  of  the  tissues,  playing 
the  rôle  of  gendarmes  in  the  organism,  constantly  in 
circulation,  always  ready  to  throw  themselves  on  every- 
thing foreign  appearing  there,  and  consequently  upon 
enemies  living  or  dead,  surrounding  by  virtue  of  this 
general  property  the  cells  of  the  microbes,  digesting 
them  and  making  them  disappear — all  that  could  not 
fail  to  captivate  him  !  The  idea  was  the  idea  of  a  biolo- 
gist and  of  a  naturalist;  it  had  not  occurred  to  Pasteur, 
but  that  did  not  prevent  him  from  welcoming  it  with 
deference.  As  long  as  he  lived,  he  wished  to  keep  in 
touch  with  its  progress. 

It  pleased  him  so  much  the  more  that  after  remaining 
for  sometime  in  the  field  of  anatomy  and  natural  history, 
the  problem  was  not  long  in  returning  to  the  field  of 
chemistry,  to  which  all  our  conceptions,  whatever  may 
be  their  objects,  provided  they  are  deep,  are  not  slow 
in  returning,  because,  at  bottom,  it  is  chemical  mutations 
which  govern  everything. 

The  theory  of  Metchnikoff  had,  moreover,  for  his 
mind,  this  satisfying  side  that  it  equalized  the  competi- 
tive forces.  There  is  something  disproportionate  in  a 
bacteridium  which  kills  an  ox.  One  understands  better 
a  localized  struggle  between  the  leucocytes  of  the  ox 
and  the  invading  microbes,  which  perish  if  they  are 
too  feeble,  or  too  few  in  number,  but  which  take  posses- 
sion of  everything  if  they  are  the  stronger,  because  they 
have  the  power  of  multiplication  in  their  favor. 

Nevertheless,  thus  limited  and  defined,  the  conditions 
of  the  struggle  remained  hazy  and  somewhat  mysterious. 


CELLULAR   THEORY   OF   IMMUNITY  319 

One   might   have   understood   a   conflict   between   the 
microbe  and  the  cells  directly  reached  by  the  inoculation 
or  located  in  its  neighborhood;  but  obedient  to  what 
mysterious  call  do  the  white  cells  come  from  all  parts  of 
the  organism,  filtering  through  vessels,  and  penetrating 
to  the  region  where  they  will  be  useful?     The  living  cells 
have  no  emotion,  not  even  that  of  well-being,  they  have 
only  needs,  and  obey  only  physical  or  chemical  actions. 
The  discovery  of  chemiotaxis,  and  the  extension  to  the 
leucocytes  of  ideas  introduced  into  science  by  Pfeiffer 
has  taken  away  from  the  theory  of  M.  Metchnikoff  a 
little  of  its  mysterious  aspect,  and  with  the  same  stroke 
has  brought  back  to  the  field  of  chemistry  the  question 
which  had  been  referred  to  the  cellular  field.     It  dem- 
onstrates the  existence  in  the  leucocyte  of  a  sort  of 
far-away    scent,  which  indicates  to  it  the  directions  in 
which  it  will  find  substances  suited  to  its  taste,  or  from 
which  it  can  derive  benefit.     These  substances  are  se- 
creted by  the  microbes  used  for  inoculation,  or  intro- 
duced with  them  in  the  bouillon  cultures.     Immediately, 
they  challenge  the  enemy  and  the  struggle  begins.     It 
can  happen,  and  in  fact  does  happen  sometimes  that  the 
secretions  of  the  bacillus  are  not  inciting,  and  even  that 
they  are  repellent.     Then   the  bacillus  protects  itself 
against  the  leucocytes,  and  can  develop  at  its  ease,  if  the 
host  does  not  put  into  play  secondary  causes  of  resistance. 
As  to  the  struggle,  when  once  begun,  its  issue  always 
rests    undecided    a  priori.     Sometimes    the  leucocyte, 
surrounds   the  microbe  and  digests  it.     It  becomes  a 
phagocyte.     Sometimes  also  the  ingested  microbe  suc- 
ceeds in  remaining  alive,  continues  to  secrete  injurious 
substances,  a  toxine,  and  it  is  the  leucocyte  which  suc- 
cumbs.    In  cases  in  which  disease  follows  the  inocula- 
tion, the  victory  remains  undecided  for  some  time,  then 
results  in  favor  of  one  of  the  adversaries. 


320  pasteur:  the  history  of  a  mind 

When  it  is  the  host  which  succumbs,  the  microbe  seems 
to  emerge  more  inured  to  the  struggle,  capable  of  secret- 
ing in  greater  abundance  the  products  which  have  ren- 
dered it  victorious.  We  explain  this  fact  by  saying  that  it 
has  become  more  virulent,  and  a  good  way  of  increasing 
its  virulence  is  to  make  it  pass  through  species,  which 
without  being  absolutely  immune,  can  resist  it  a  long 
time  and  enable  it  to  acquire  a  new  vigor.  That  is  what 
we  did  when  we  rendered  the  anthrax  bacteridium  more 
virulent  by  making  it  pass  through  species  more  and  more 
resistant  to  its  action. 

On  the  other  hand,  when  it  is  the  microbe  which  suc- 
cumbs in  the  struggle,  the  leucocytes  in  their  turn  issue 
from  the  conflict  stronger,  more  sensitive  to  the  chem- 
iotaxis  of  the  microbes  which  they  have  killed,  and  more 
accustomed  to  their  toxines,  and  the  animal  consequently 
has  a  power  of  resistance,  an  immunity,  which  it  did  not 
formerly  possess. 

It  is  not  necessary  to  enter  into  details  to  see  that  we 
have  here  a  conception  which  lends  itself  in  a  remarkable 
manner  to  the  interpretation  of  all  the  very  curious  facts 
discovered  by  Pasteur.  I  add  that  this  interpretation 
is  not  purely  theoretical.  It  is  sufficient  to  read,  in  the 
Annales  de  l'Institut  Pasteur,  the  numerous  works  ac- 
cumulated on  this  subject  by  M.  Metchnikoff  and  his 
pupils,  to  be  convinced  that  we  are  face  to  face  not  only 
with  a  captivating  theory,  but  with  a  theory  true  to  its 
smallest  details,  and  in  all  respects  fruitful. 

In  résumé,  the  resistance  of  each  living  being  with 
respect  to  a  microbial  inoculation  is  at  the  same  time 
a  question  of  species,  a  question  of  individuals,  a  question 
of  place  and  of  time,  a  question  of  quantity  of  inoculating 
material,  and  also  a  question  of  temperature,  for  a  low- 
ering of  temperature  can  diminish  the  activity  of  the 
leucocytes  and  increase  that  of  the  bacillus,  as  in  case 


CELLULAR   THEORY   OP   IMMUNITY  321 

of  the  chicken  which,  when  chilled,  contracted  anthrax. 
A  microbe  may  be  harmless  for  the  species  which  carries 
it,  and  may  not  be  so  for  others,  the  resistance  of  which 
is  not  organized  in  the  same  fashion.  It  will  be  under- 
stood that  it  may  be  fatal  to  the  young  animal,  whose 
phagocytes  are  not  inured,  that  it  may  develop  where 
the  phagocytes  are  not  numerous,  and  not  where  it 
finds  them  in  great  numbers  and  better  trained,  etc. 
And  all  this  happens  through  the  intermediary  of  cel- 
lular secretions,  that  is  to  say  through  physico-chemical 
agencies.  It  is  evident  that  Claude  Bernard  and  the 
physiologists  who  feared  to  see  Pasteur  re-introduce  into 
science  the  idea  of  life  as  a  hidden  cause  had  in  him 
not  an  enemy  of  their  doctrines,  but  a  powerful  ally. 
We  see  also  that  the  physicians  were  right  in  treating 
him  as  a  chemist.  They  were  wrong  only  in  pronouncing 
this  name  with  a  disdainful  air.  With  Pasteur  chemistry 
took  possession  of  medicine  and  we  can  foresee  that  it 
will  not  relinquish  its  hold. 


21 


PASTEUR 

(Photo,  by  the  writer,  from  a  bronze  plaque  by  G.  Prud'homme.) 

(Courtesy  of    Col.  J.  F.  Siler,  Office  of    the  Surgeon  General, 
Washington,  D.  C.) 


ANNOTATED  LIST  OF  PERSONS  MENTIONED  IN  THIS  BOOK 

{The  following  statements  have  been  derived  principally  from  French, 
Italian,  and  German  sources.  In  a  few  instances  I  have  taken  dates 
from  Garrison's  "History  of  Medicine"  (W.  B.  Saunders  Co.,  2d  edition, 
1917).  This  book  contains  an  appendix  entitled  "  Medical  Chronology," 
very  useful  to  students  in  fixing  dates  of  various  important  discoveries 
in  pathology  and  bacteriology.  It  contains  also  portraits  of  many  of 
the  persons  here  mentioned,  and  to  these  portraits  I  have  referred  as 

"Garrison,  p. ."     The  book  is  very  readable  and  is  recommended  to  all 

students,  even  those  not  interested  in  medicine.  They  cannot  read 
it  without  becoming  so.  The  other  abbreviated  portrait  references, 
not  self-explanatory,  are  of  Pagel's  very  interesting  "  Biographisches 
Lexikon  hervorragender  Àrzte  des  neunzehnten  Jahrhunderts,"  Berlin 

and  Vienna,  1901,  referred  to  as  "Pagel,  p. ,"  Werckmeister's  "Das 

neunzehnte   Jahrhundert  in    Bildnessen,"  5  vols.    (1898-1901),  Berlin, 

Photog.  Gesellschaft,  referred  to  as  "  Werckmeister,  p. ,"  Veit  Brecher 

Wittrock's  Catalogus  illustratus  iconothecae  botanicae  horti  Bergiani 
Stockholmiensis,  Pars  I  and  II.  Acta  Horti  Bergiani.  Bd.  3,  Nos.  2 
and  3,  Stockholm,  1903  and  1905,  referred  to  as  "Wittrock  I,  or  II,  Tafl. 
"  and  "  Histoire  illustrée  de  la  Littérature  Française  Précis  Méthodi- 
que." Par  E.  Abry,  C.  Audic,  P.  Crouzet.  3e  Edition  revue  et  corrigé. 
Paris.  Henri  Didier,  Éditeur.  1916,  pp.  XII,  664.  A  copiously  illus- 
trated, inexpensive  and  fascinating  beginner's  book  of  French  literature, 

referred  to  as  "Abry  p. ." 

Appert,    Emile    ( -  ).     French  mathematician    and    chemist. 

First  science  teacher  of  Duclaux. 

Appert,  François  (17 1840.)     French  manufacturer.     Brother  of  the 

philanthropist.  Invented  canning  for  the  preservation  of  foods. 
Received  12,000  francs  from  the  French  Government  for  making 
public  his  discovery.  His  book  (1810)  entitled  "Le  livre  de  tous 
les  ménages,  ou  l'art  de  conserver  pendant  plusieurs  années  toutes 
les  substances  animales  et  végétales,"  passed  through  five  editions. 
Arloing,  Saturnin  (1846-1911).  French  physician  and  veterinarian. 
Professor  of  experimental  medicine  at  Lyons.  Studied  sympto- 
matic anthrax  with  Cornevin  and  Thomas.  Investigated  peri- 
pneumonia, etc.  Wrote  an  "Anatomy  of  domestic  animals" 
which  passed  through  four  editions. 
Bacon,  Frances  Lord  Verulam  (1561-1623).  English  judge  and  natural 
philosopher.  His  "Novum  Organum"  was  published  in  London 
in  1620. 

"The  wisest,  brightest,  meanest  of  mankind."     (Pope.) 
323 


324  ANNOTATED    LIST   OF   PERSONS 

BaU,  Karl  Adolph  Emmo  Theodor  (1833 ).     German  mycologist. 

Discovered  the  submerged  yeast  form  of  Mucor  mucedo. 

Balard,  Antoine  Jérôme  (1802-1876).  French  chemist.  Born  in 
Montpellier.  Professor  in  the  Normal  School,  the  College  of  France 
and  the  Sorbonne.  Inspector  general  of  higher  education.  Member 
of  the  Academy  of  Sciences.  Discovered  bromine  (1826)  and 
succeeded  in  extracting  sodium  sulphate  from  sea  water. 

"Par  sa  chaleur  d'âme,  il  entraînait  tout  le  monde  daDS  un  mouve- 
ment généreux.  C'était  un  éveilleur  d'activités.  ...  Ce  qui  me 
charmait  en  lui,  c'est  qu'il  avait  le  culte  de  la  science  pure.  Dès 
qu'un  homme  de  laboratoire  mêle  à  ses  travaux  d'autres  préoccupa- 
tions, il  est  arrêté  dans  sa  marche."     (Pasteur.) 

Barbet   ( ).     Director  of  the  "Maison  Barbet,"  a  Parisian 

preparatory  school.     Teacher  of  Pasteur  and  of  Duclaux. 

Bastian,  Henry  Charlton  (1837-1915).  English  physician,  physiologist 
and  pathologist.  Born  in  Cornwall.  Professor  in  University  of 
London.  Member  of  the  Royal  Society.  Bastian  wrote  "The 
Modes  of  Origin  of  Lowest  Organisms"  (1871),  "The  Beginnings  of 
Life"  (1872),  and  "Studies  in  Heterogenesis "  (1901).  Student 
of  nematodes  and  of  the  brain  and  nervous  system.  Adversary 
of  Pasteur.     For  portrait  see  Pop.  Sci.  Monthly,  Nov.,  1875. 

Beal,    William   James    (1833 ).     American   botanist.     Born    in 

Michigan.     Student  of  Louis  Agassiz  and  of  Asa  Gray.     For  many 
years  professor  in  Michigan  Agricultural  College. 

Béchamp,  Pierre  Jacques  Antoine  (1816-1908).  French  physician. 
Professor  in  Faculty  of  Medicine  in  Montpellier  and  afterward  in 
the  Catholic  Faculty  in  Lille.  Antagonist  of  Pasteur.  Copious 
writer.  His  chief  work  is  "Les  Microzymas  dans  leurs  rapports 
avec  l'hétérogénie,  l'histogénie,  la  physiologie  et  la  pathologie, 
examen  de  la  panspermie  atmosphérique  continue  ou  discontinue, 
morbifère  ou  non  morbifère,"  8  vo.,  pp.  992,  Paris  (1883);  see  also 
"Microzymas  et  Microbes"  (1888). 

"As  to  the  nature  of  the  disease  [flacherie]  and  its  cause,  M.  Bé- 
champ ascribes  it  to  mobile  molecules  which  he  calls  microzymas 
and  which  he  sees  swarming  everywhere  'on  the  surface  of  the 
worms,  in  their  fluids,  in  the  eggs,  etc'  I  leave  to  M.  Béchamp 
the  complete  priority  of  these  facts."     (Pasteur.) 

Bêcher,  Johann  Joachim  (1635-1682).  German  chemist  and  political 
economist.  A  forerunner  of  Stahl.  Helped  to  introduce  potato- 
culture  into  Germany — a  vast  undertaking,  since  there  was  a  strong 
popular  prejudice  to  be  overcome. 

Beethoven,  Ludwig  van  (1770-1827).  Greatest  of  composers.  Son  of  a 
drunkard  who  was  a  mediocre  musician  and  of  a  tuberculous  woman 
who  was  the  daughter  of  a  cook.     Generally  reckoned  as  a  German, 


ANNOTATED    LIST   OF   PERSONS  325 

but  his  masque  shows  Slavic  features.  He  was  bom  in  Bonn  on 
the  Rhine.  His  father's  father  came  from  the  low  countries 
(Antwerp),  and  his  mother's  maiden  name  was  Maria  Magdelena 
Kewerich.  He  was  an  upright,  democratic  man,  passionately  fond 
of  nature  and  what  is  best  in  music,  literature  and  art.  He  wrote 
German  badly,  but  in  music  he  was  a  god!  He  spent  most  of  his 
mature  life  in  Vienna  and  died  there.  For  portraits  see  "Beethoven" 
by  Vincent  d'Indy  in  "Les  Musiciens  Célèbres"  Paris,  Renouard, 
and  "Beethoven,  the  man  and  the  artist  as  revealed  in  his  own 
words,"  by  Fr.  Kerst  (Tr.  by  Krehbiel.  N.  Y.,  B.  W.  Huebsch,  but 
without  the  portraits). 
Bellamy, 

Bellotti,  Cristoforo  ( ).     Italian  student  of  silk- worm  diseases 

in  the  Museo  Civico  of  Milan.  Published  several  papers  in  Milan 
(1863-1879).     Wrote  also  on  the  fossil  fish  of  Lombardy. 

Berkeley,  Rev.  Miles  Joseph  (1803-1889).  English  microscopist  and 
cryptogamic  botanist.  Author  of  "British  Fungi,"  "Decades  of 
Fungi,"  "Introduction  to  Cryptogamic  Botany,"  "Handbook  of 
British  Mosses,"  etc.  Wrote  also  on  diseases  of  plants  for  "The 
Gardeners'  Chronicle."  For  portraits  see  Wittrock  II,  Tafl.  145, 
and  Whetzel's  History  of  Phytopathology,  p.  56. 

Bernard,  Claude  (1813-1878).  Distinguished  French  physiologist. 
Magendie's  assistant.  Professor  in  Paris.  Member  of  the 
Academy  of  Sciences  and  of  the  Académie  Française.  Senator. 
Discovered  action  of  the  pancreas  in  the  digestion  of  fat,  storage  of 
glycogen  in  the  liver,  existence  of  nervous  centers  acting  independ- 
ently of  the  brain  and  cord  (sympathetic  system),  and  sugar  in 
the  urine  as  a  result  of  wounding  the  fourth  ventricle  of  the  brain. 
Author  of  many  books  and  papers.  His  "Leçons  sur  les  phénomènes 
de  la  vie  commune  aux  animaux  et  aux  végétaux"  appeared  in 
Paris  in  1879.  For  portraits  see  Garrison,  p.  576,  Pagel,  p.  147, 
Abry,  p.  589  and  Pop.  Sci.  Monthly,  Oct.  1878. 

Bert,  Paul  (1833-1886).  French  politician  (Republican)  and  physi- 
ologist. Student  of  Claude  Bernard.  Professor  in  Bordeaux  and 
in  Paris.  Received  20,000  francs  reward  for  barometric  investiga- 
tions in  relation  to  fife  processes.  Member  of  Gambetta's  ministry. 
Pasteur's  friend.  Wrote  "Leçons  sur  la  physiologie  comparée 
de  la  respiration,"  8vo,  pp.  xxxv,  588.  Paris,  1870.  Dedicated 
to  Claude  Bernard.  For  portraits  see  Harper's  Mag.,  1882,  p.  560, 
and  Pop.  Sci.  Monthly,  July,  1888. 

Berthelot,  Marcelin  Pierre  Eugene  (1827-1907).  French  chemist. 
Senator.  Remarkable  for  his  studies  of  organic  substances: 
polyatomic  alcohols;  synthesis  of  organic  substances;  thermo- 
chemistry; explosives.     Assistant  of  Balard.     Professor  in  School  of 


326  ANNOTATED    LIST   OF    PERSONS 

Pharmacy  and  College  of  France.  Member  of  the  Institute. 
Author  of  many  books  and  papers.  His  "La  synthèse  chimique" 
passed  through  eight  editions.  For  portraits  see  McClure's  Maga- 
zine, 1894,  p.  305,  and  Pop.  Sci.  Monthly,  May,  1885. 

Bertin,  Pierre  Augustin  (1818-1884).  French  physicist.  Student  in 
the  Normal  School.  Professor  in  Strassburg.  Professor  in  the 
Normal  School:  master  of  conferences  and  sub-director.  Friend 
of  Pasteur.  For  portrait  see  "Le  Centenaire  de  l'École  normale." 
Paris,  1895,  p.  400. 

Berzelius,  John  Jacob  (1779-1848).  Swedish  physician  and  chemist. 
Professor  in  Stockholm.  Introduced  symbolic  notation,  determined 
atomic  weights,  developed  the  doctrine  of  valency.  Studied  and 
developed  electrolysis  :  in  the  decomposition  of  water  showed  that 
hydrogen,  metals  and  alkalies  go  to  the  negative  pole,  and  oxygen 
and  acids  to  the  positive  pole  of  the  battery.  Discovered  selenium 
and  cerium;  showed  calcium,  barium,  strontium,  tantalium,  silicium 
and  zirconium  to  be  elements;  investigated  whole  classes  of  com- 
pounds. Author  of  many  papers  and  books,  including  an  annual 
review  of  the  progress  of  chemistry  and  mineralogy  for  27  years. 
One  of  the  fathers  of  modern  chemistry.  For  portrait  see  Harper's 
Mag.,  1897,  vol.  95,  p.  756. 

Biot,  Jean-Baptiste  (1774-1862).  French  physicist,  mathematician  and 
astronomer.  His  chief  contributions  were  in  optics.  Associate 
of  Gay-Lussac  and  Arago.  A  brave  and  just  man.  Very  helpful 
to  the  young  Pasteur.  For  portraits  see  L'Art,  1876,  p.  183,  Art 
and  Letters,  1881,  p.  187,  and  Harper's  Mag.,  1897,  p.  49. 

Black,  Joseph  (1728-1799).  Scotch  chemist.  Professor  in  Edinburgh. 
Foreign  member  of  the  French  Academy  of  Sciences.  A  forerunner 
of  Cavendish  and  Priestley.  Studied  alkalies  and  alkaline  earths. 
Discovered  latent  heat  and  "fixed  air"  (carbon  dioxide).  One 
of  the  creators  of  modern  chemistry.  For  portrait  see  Garrison, 
p.  323. 

Blanchard,  Emile  (1820-1900).  French  naturalist.  Professor  in  the 
National  Agronomic  Institute.  President  of  the  Academy  of 
Sciences  in  1881.     Wrote  a  natural  history  of  insects,  etc. 

Bloch,  Gustave  (1848 — ).     French  historian.     Professor  in  Besançon, 

Lyons  and  Paris.     Officer  of  the  Legion  of  Honor.     French  normal 
school  graduate.     Eulogist  of  Duclaux. 

Bornet,  Jean  Baptiste  Edouard  (1828-1912).  French  algologist.  Mem- 
ber of  the  Academy  of  Sciences.  Contributed  much  to  our  knowl- 
edge of  red  algae  and  lichens.  Collaborated  for  many  years  with 
Thuret.  For  portraits  see  Wittrock  I,  Tan.  33,  and  Wittrock  II, 
Tan.  83. 


ANNOTATED    LIST   OF   PERSONS  327 

Bouley,  Henri  (1814-1885).  French  veterinarian  and  comparative 
pathologist.  Member  of  the  Institute.  President  of  the  Academy 
of  Sciences  in  1885.  Champion  of  Pasteur.  For  a  portrait  see 
Rec.  Méd.  Vét.,  7  sér.,  Tome  II,  No.  23,  15  dec,  1885. 

Boullay,  Polydore  (1806-1835).  French  chemist.  Wrote  "Mémoire 
sur  la  formation  de  l'éther  sulfurique"  (1827),  "Mémoire  sur  les 
éthers  composés"  (1828). 

Boussingault,  Jean  Baptiste  Joseph  Dieudonné  (1802-1887).  French 
analytical  and  agricultural  chemist.  Fought  under  Bolivar  in 
South  America.  Climbed  Chimborazo  (1831).  Professor  in  Lyons 
and  in  Paris.  Member  of  the  Academy  of  Sciences;  Member  of  the 
National  Assembly  (1848).  Grand  officer  of  the  Legion  of  Honor. 
He  showed  that  ordinary  plants  cannot  assimilate  free  nitrogen. 
One  of  the  founders  of  the  Science  of  Agronomy  (see  his  "Traité 
d'Économie  rurale"  and  his  "Agronomie,  chimie  agricole,  et 
physiologie").  For  portraits  see  Wittrock  II,  Tafl.  58,  and  Pop.  Sci. 
Monthly,  Oct.,  1888. 

Boutron,  Charlard  Antoine   François  (1796-1878).     French  chemist. 

Boyle,  Robert  (1627-1691).  English  chemist  and  physicist.  Brother 
of  the  statesman.  Discovered  Boyle's  law.  Wrote  his  "  Sceptical 
chymist"  in  1661.  Used  vegetable  colors  for  determining  acidity 
and  alkalinity  of  solutions;  invented  a  freezing  mixture.  Founded 
a  lectureship  on  the  Evidences  of  Christianity.  For  portrait 
see  Pop.  Sci.  Monthly,  Feb.,  1893. 

Brauell,  J.  Fr.  ( ■ ) .    German  veterinarian  at  Dorpat.     Brau ell's 

first  communication  appears  to  have  been  in  Virchow's  Archiv, 
1857.     Wrote  also  on  rinderpest  (1862). 

Bremer,  Gustav  Jacob  Wilhelm  (1847-1909).  Dutch  chemist.  Taught 
in  Rotterdam.  Published  in  Dutch  a  paper  on  malic  acid  (Een 
rechtsdraaiend  appelzuur)  in  1875. 

Broussais,  François  Joseph  Victor  (1772-1838).  French  physician  and 
pathologist.  Founder  of  a  school  of  medicine  called  "the  physio- 
logical school,"  which  for  a  time  had  an  enormous  following  in 
France.  Broussais  was  a  great  believer  in  the  value  of  starvation 
and  blood-letting.  He  would  cover  a  patient  with  leeches.  For 
portraits  see  Garrison,  p.  416,  and  Pagel,  p.  29. 

Brucke,  Ernst  Wilhelm  Ritter  von  (1819-1892).  German  anatomist  and 
physiologist.  Professor  in  Koenigsberg  and  Vienna.  Author  of 
numerous  papers  on  physiology  of  speech,  physiology  of  colors, 
etc.     For  portraits  see  Garrison,  p.  489,  and  Pagel,  p.  259. 

Buffon,  George  Louis  Leclerc  de  (1707-1788).  French  naturalist. 
Celebrated  for  the  style  of  his  books,  which  were  translated  into 
many  languages  but  are  of  slight  value  now.     It  was  he  who  said: 


328  ANNOTATED   LIST   OF   PERSONS 

"Le  style  est  l'homme  même."  For  portraits  see  Abry,  p.  387 
and  Petit  Larousse  illustré,  p.  1193. 

Burdon-Sanderson,  Sir  John  Scott  (1828-1905).  English  physician 
and  physiologist.  Lecturer  at  St.  Mary's  Hospital.  Professor  in 
London  University  and  University  College  of  London.  Member 
of  the  English  Rabies  Commission  (1886). 

Cagniard-Latour  (or  de  la  Tour)  (1777-1859).  French  physicist. 
Invented  the  siren  whistle  (1809),  called  in  French  cagniardelle. 

Cantani,  Arnaldo  (1837-1893).  Italian  physician,  clinician  and  pa- 
thologist. Son  of  a  Neapolitan  physician.  Senator.  Professor  in 
Pavia  and  then  in  University  of  Naples.  Author  of  several  books. 
Interested  especially  in  infectious  diseases.  Wrote  on  cholera. 
For  portrait  see  Pagel,  p.  303. 

Cantoni,  Gaetano  (1815-1887).  Italian  student  of  silkworm  diseases. 
Professor  in  the  Royal  Museum  in  Turin.  Founder  and  director 
of  the  High  School  of  Agriculture  in  Milan.  Author  of  many  books 
and  papers  on  agricultural  subjects.  Wrote  "Trattato  completo 
teorico-pratico  di  agricoltura,"  3d  éd.,  2  vols.,  Milan,  1884-5. 

Chamberland,  Charles  Edouard  (1851-1908).  French  physicist,  pa- 
thologist and  bacteriologist.  Normal  school  graduate.  One  of 
Pasteur's  collaborators.  Member  of  the  Legion  of  Honor.  Col- 
laborated also  with  Roux,  Joubert,  Strauss,  Fernbach  and  Jouan. 
Elected  radical  Republican  Deputy  from  the  Jura  in  1885.  Author 
of  several  independent  works:  "Origin  and  Development  of  Micro- 
scopic Organisms"  (1879),  "Drinking  Waters  and  Epidemic 
Diseases."  Invented  the  Chamberland  filter  (1884).  For  portrait 
see  "Ann.  d  l'lnst.  Pasteur,"  May,  1908. 

Chantemesse,  André  (1851 — ).     French  physician.  Professor  in  the 

Faculty  of  Medicine.  Officer  of  the  Legion  of  Honor.  Author 
of  "Mosquitos  and  Yellow  Fever,"  "Flies  and  Cholera,"  "Traité 
d'hygiène,"  etc.  Collaborated  in  anti-rabic  inoculations  at  Pasteur 
Institute.     One  of  the  Editors  of  "Ann.  de  l'lnst.  Pasteur." 

Charrin,  Albert  (1857-1907).  French  physician.  One  of  the  discoverers 
of  the  glanders  bacillus  (Bouchard,  Capitan  et  Charrin,  "C.  R. 
Acad.  d.  Sci.,"  Dec.  26,  1882).  Collaborated  in  anti-rabic  inocula- 
tions at  Pasteur  Institute.  Author  of  "Les  defenses  naturelles 
de  l'organisme"  (Paris,  1898). 

Chassang,  Alexis  (1827-1888).  French  grammarian,  lexicographer  and 
litterateur.  Author  of  many  books — grammars,  dictionaries, 
anthologies. 

Chauveau,  Jean  Baptiste  Auguste  (1827-1917).  Distinguished  French 
veterinarian,  anatomist,  physiologist  and  pathologist.  Commander 
of  the  Legion  of  Honor.     Member  of  the  Academy  of  Sciences  and  of 


ANNOTATED    LIST   OF   PERSONS  329 

the  Academy  of  Medicine.     Editor  of  the  "  Journal  de  Physiologie 
et  de  Pathologie  Générale"  and  "La  Revue  de  la  Tuberculose." 
Author  of  the  classical  "Traité  d'anatomie  descriptive  des  animaux 
domestiques."     For  portraits  see  "The  Veterinary  Journal,"     Lon- 
don, vol.  73,  No.  2,  Feb.,  1917.     "Journal  de  Physiol,  et  de  Path. 
Générale."     Tome  XVII,   No.   1.     Paris,   1917,  and   "Recueil  de 
Médecine  Vétérinaire,"  Tome  XCIII.    Nos.  1-2,  Paris,  1917. 
Cohn,    Ferdinand    Julius    (1828-1898).     German   botanist.     Professor 
in  Breslau.     Studied  mostly  the  morphology  and  developmental 
history  of  algae,  fungi  and  bacteria.     Born  and  died  in  Breslau. 
For    portrait    in    age   see    "Bact.    in    Rel.    to    Plant    Diseases," 
Carnegie  Inst,  of  Washington,  vol.  I,   (Frontispiece)  and  at  33, 
Wittrock  II,  Tafl.  84. 
Collin, 
Columella,  Lucius  Junius  Moderatus.     Roman  poet  of  the  First  Century. 

Wrote  " De  re  rustica"  (12  books  in  dactylic  hexameters). 
Cornalia,     Ser    Emilio     (1824-1882).     Italian    zoologist.     Student   of 
silkworm  diseases.     Wrote  a  monograph  on  the  Bombyx  of  the 
mulberry  (Milan,  1856).     Discovered  "Cornalia  bodies"  (Nosema 
bombycis    Nâgeli,  Panhistophyton  ovale  Lebert),  cause  of  pébrine. 
Wrote  also  on  geology. 
Cornevin,  Charles  Ernest  (1846-1897).     French  pathologist.     Student 
of  symptomatic  anthrax  with  Arloing  and  Thomas.     Wrote  also 
on  "rouget,"  and  a  book  on  poisonous  plants  (Paris,  1893). 
Coze,  Léon  (1817-1896).     French  pathologist. 

Darwin,    Charles   Robert    (1809-1882).     English   naturalist.     A  great, 

simple-minded,    humble    and    lovable    man.     Probably    the    most 

influential  person  in  the  nineteenth  century.     His  greatest  book 

"The  Origin  of  Species  by  Means  of  Natural  Selection"  was  published 

in  1859.     For  portraits  see  Wittrock  II,  Tafl.  65,  Garrison,  p.  540, 

Pagel,  p.  33,  and  Pop.  Sci.  Monthly,  Feb.,  1873,  and  Nov.,  1901. 

Davaine,    Casmir   Joseph  (1812-1882).     Illustrious   French  physician, 

zoologist  and  pathologist.     Student  of  anthrax.     Member  of  the 

Academy  of  Medicine.     Author  of  a  "Traité  des  entozoaires  et  des 

maladies  vermineuses  de  l'homme  et  des  animaux  domestiques" 

(2d  éd.,  8  vo.,  Paris,  1878).     For  portrait  see  "Arch.  d.  Parasit.," 

T.  7,  p.  123. 

Dechambre,    Amédêe    (1812-1886).     French    physician.     Member  of 

the  Academy  of   Medicine.     Chevalier  of  the  Legion  of  Honor. 

Wrote  on  "Diseases  of  Old  Age,"  etc.     His  vast  "Diet,  encycl. 

des  Sci.  Médicales"  (1864-90)  includes  100  volumes. 

Dêclat,  Gilbert  (1827-1896).     French  physician.     Following  Pasteur's 

studies  on  fermentation  he  made  early  use  of  antiseptics  in  medicine 


330  ANNOTATED    LIST   OF   PERSONS 

and  surgery.  Edited  from  1874  a  journal  for  the  diffusion  of  his 
ideas  called  "Médecine  des  ferments." 

Delafond,  Onésime  (1805-1861).  French  veterinarian.  Professor  in 
the  school  at  Alfort.  Member  of  the  Academy  of  Medicine.  Dela- 
fond was  appointed  to  study  anthrax  in  sheep  in  1841.  His  "Traité 
sur  les  maladies  du  sang  des  bêtes  à  laine"  was  published  in  Paris 
in  1845.  His  second  book  "Traité  sur  la  maladie  du  sang  des 
bêtes  bovines"  appeared  in  1848.  Delafond's  anthrax  paper  of 
1860  referred  to  in  the  text,  is  in  "Recueil  de  Méd.  Vétér.,"  1860, 
p.  735. 

Delafosse,   Gabriel   (1796-1878).     French  mineralogist  and  crystallog- 
rapher.     Pupil  of  Hatiy.     Pasteur's  teacher  in  the  Normal  School. 
Member  of  the  Academy  of  Sciences. 
"Un  homme  qui  avait  le  don  de  l'enseignement."     (Pasteur.) 

Descartes,  René  or  Renatus  Cartesius  (1596-1650).  Distinguished 
French  geometer,  physicist  and  philosopher.  Created  analytic 
geometry.  Destroyed  scholasticism  and  founded  modern  psy- 
chology. Author  of  the  "Cartesian"  system.  Cogito,  ergo  sum  was 
his  foundation  stone.  From  this  he  derived  two  other  fundamental 
ideas,  the  existence  of  God  and  the  reality  of  an  external  world. 
According  to  his  "corpuscular  philosophy,"  all  phenomena  of 
matter  depend  on  the  movement  of  ultimate  particles.  Beginning 
with  1629  he  lived  20  years  in  retirement  outside  of  France  working 
on  his  system.  Died  in  Stockholm.  For  portraits  see  Garrison,  p. 
247,  Abry,  p.  130  and  Pop.  Sci.  Monthly,  Oct.,  1890. 

Desmazières,  Jean  Baptiste  Henri  Joseph  (1786-1862).  French  botanist 
and  microscopist,  especially  noted  for  his  "Plantes  cryptogames  de 
France"  (1825-1859).  Desmazières  acquired  a  fortune  in  business, 
which  he  used  for  the  study  of  science.  For  portrait  see  "Bull, 
de  la  Soc.  Mycologique  de  France."     Tome  XX.  Paris,  1904. 

Dessaignes,  Victor  (1800-1885).  French  chemist  in  Vendôme.  Cor- 
responding member  of  the  Academy  of  Sciences  in  chemistry. 

Deville  (See  Sainte-Claire-Deville). 

Dôbereiner,  Johann  Wolfgang  (1780-1849).  German  chemist.  Pro- 
fessor in  Jena.     Friend  of  Goethe. 

Dreyfus,  Alfred   (1859 ).     French  Captain  of  Artillery.     A  Jew. 

Falsely  accused  by  military  men  and  anti-Semites  of  selling  or 
giving  military  secrets  to  Germany.  Arrested  (1894),  condemned, 
degraded  (1895),  and  sent  for  life  to  Devil's  Island  in  the  Atlantic 
near  French  Guiana.  The  effort  on  the  part  of  the  French  liberals 
to  free  him  and  convict  the  really  guilty  parties,  who  were  other 
military  officers  (Major  Esterhazy  and  Colonel  Henry),  nearly 
disrupted  the  French  Government,  but  was  finally  successful,  and 
Col.  Henry  committed  suicide.     Zola  defended  Dreyfus  in  "L'affaire 


ANNOTATED   LIST   OF   PERSONS  331 

Dreyfus."  With  the  exception  of  the  noble  and  brave  Col.  Picquart, 
the  French  war  department  chiefs,  almost  to  a  man,  insisted  on  his 
guilt,  even  after  his  innocence  was  established,  and  they  were  ably  sup- 
ported in  their  iniquity  by  the  clergy,  religious  orders,  and  all 
anti- Jewish  influences.  The  authorities  refused  to  reopen  the  case; 
Col.  Picquart  was  ordered  to  Tunis  and  subsequently  imprisoned; 
Esterhazy,  who  had  been  accused  by  Dreyfus,  was  tried  by  court 
martial  behind  closed  doors  and  acquitted;  Zola  was  prosecuted 
and  convicted,  and  fled  from  Paris;  and  Dreyfus,  finally  retried  by 
court  martial  at  Rennes,  was  again  convicted  but  with  "extenuating 
circumstances;"  Maître  Labori,  his  leading  attorney  was  shot 
during  the  trial;  the  President  of  France  was  insulted;  and  Paul 
Déroulède,  the  poet,  urged  the  military'  to  destroy  the  republic. 
The  injustice  of  the  judgment  at  Rennes  was  so  apparent  and  so 
flagrant  that  Dreyfus  was  pardoned  (1899),  but  all  France  was  in  a 
ferment  which  did  not  subside  for  several  years.  Dreyfus  demanded 
another  trial  which  was  finally  granted  in  1905  and  this  time  he 
was  fully  acquitted.  Dreyfus  and  Picquart  were  then  restored 
to  the  army  with  promotions  and  when  Clemenceau  selected  his 
first  cabinet  he  made  General  Picquart  minister  of  war.  The  dis- 
establishment of  the  French  church  and  the  abolition  of  the  religious 
orders,  as  dangerous  to  the  republic,  was  a  direct  consequence  of  the 
Dreyfus  affair. 

Du  Bois-Reymond,  Emile  (1818-1896).  German  physiologist  and 
philosopher,  of  Swiss-French  extraction.  Author  of  many  books. 
"  Ignorabimus  "  is  his  famous  word.  Born  and  died  in  Berlin. 
His  brother  Paul  was  a  mathematician.  For  portraits  see  Garrison, 
p.  564,  Pagel,  p.  210,  and  Pop.  Sci.  Monthly,  July,  1878. 

Dubouê,  ( ).     French  physician.     Early  student  of 

rabies. 

Duclaux,  Emile  (1840-1904).  French  chemist,  bacteriologist,  patholo- 
gist and  rural  economist.  Director  of  the  Pasteur  Institute 
from  1895-1904,  and  closely  associated  with  it  from  its  beginning 
in  1888.  For  a  bibliography  of  Duclaux's  writings  (220  titles 
including  9  books,  two  of  which  are  on  milk)  see  the  appendix 
to  Dr.  Roux's  Review  of  Duclaux's  work  in  "Ann.  de  l'lnst.  Pasteur," 
No.  6,  1904,  pp.  354-362. 

"Les  amis  qui  ont  été  le  plus  mêlés  à  son  existence  n'ont  jamais 
surpris  en  lui  la  moindre  défaillance  morale;  il  reste  pour  eux  le 
modèle  auquel  ils  voudraient  ressembler."     (Dr.  Roux.) 

Duclaux,  Madame  Mary    (1857 ).     English  literary  woman,  née 

Agnes  Mary  Robinson,  wife  of  James  Darmesteter,  the  French 
orientalist,  then  of  Emile  Duclaux  (1901).  Poet  and  prose  writer 
in  English  and  French.     Author  of  many  books. 


332  ANNOTATED    LIST   OF   PERSONS 

Duclaux,  Pierre  Justin  (1798-1860).     Father  of  Emile  Duclaux. 

Dujardin,  Félix  (1801-1860).  French  zoologist,  student  of  Vermes, 
Rhizopods,  etc.  He  left  unfinished  a  "Natural  History  of 
Echinodermes." 

Dumas,  Jean  Baptiste  André  (1800-1884).  French  chemist.  Member 
of  the  Academy  of  Sciences.  Professor  in  the  Sorbonne,  Minister 
of  Agriculture  and  Commerce.  Senator.  Succeeded  Guizot  in 
the  Académie  Française  and  was  followed  by  Renan.  Determined 
the  atomic  weight  of  many  elements.  Studied  amyl  alcohol; 
discovered  the  law  of  substitutions,  which  upset  the  ideas  of  Berzelius. 
Published  a  great  treatise  (in  8  volumes)  on  applied  chemistry. 
For  portraits  see  Harper's  Mag.,  1898,  p.  625,  and  Pop.  Sci.  Monthly, 
1880,  p.  145. 

"I  attend  at  the  Sorbonne  the  lectures  of  M.  Dumas,  a  celebrated 
chemist.  You  cannot  imagine  what  a  crowd  of  people  come  to  these 
lectures.  The  room  is  immense,  and  always  quite  full  *  *  * 
there  are  always  six  or  seven  hundred  people."     (Pasteur  in  1842.) 

"Le  premier  banc  était  réservé  aux  élèves  de  l'École  normale. 
J'écoutais,  j'applaudissais,  je  sortais  de  chacune  de  ces  leçons 
l'esprit  tourné  vers  de  vaste  projets."     (Pasteur  in  1895.) 

Dusch,    Theodor    Freiherr    von    (1824 ).     German   pathologist. 

Student  of  Henle.  Professor  in  Heidelberg.  Wrote  on  Icterus, 
brain  sinus  thrombosis,  and  diseases  of  the  heart.  Collaborated 
with  H.  Schroder  in  the  discovery  of  cotton  as  a  dry  (air)  filter 
for  bacteria  ("Ueber  Filtration  der  Luft  in  Beziehung  auf  Fâulniss 
und  Gàhrung."  Ann.  der  Ch.  u.  Pharm.,  Bd.  89,  p.  232,  Heidelberg, 
1854).     For  portrait  see  Pagel,  p.  431. 

Duval,  or  Duval-Jouve,  Joseph  (1810-1883).  French  botanist.  Studied 
Equisetums  and  anatomy  of  grasses.  Father  of  the  anatomist. 
For  portrait  see  Wittrock  II,  Tafl.  138. 

Ehrenberg,  Christian  Gottfried  (1795-1876).  German  medical  man, 
naturalist  and  traveler.  Author  of  many  elaborate  and  important 
works  on  microscopic  organisms,  partly  in  Latin,  and  many  of 
them  magnificently  illustrated.  Ehrenberg  discovered  fossil  in- 
fusoria and  laid  the  foundations  of  our  knowledge  of  this  group  of 
animals.  Traveled  with  Humboldt  in  Asia  and  with  Hemprich 
in  Egypt.  Opposed  to  the  theory  of  spontaneous  generation. 
For  portraits  see  Pop.  Sci.  Monthly,  March,  1879,  and  Werck- 
meister,  1901,  5,  pi.  481. 

Fabroni,  J.  Valentin  (1752-1822).     Italian  chemist  and  engineer. 

Farges,  Agnès  ( •)•     Mother  of  Emile  Duclaux. 

"Tous  les  mendiants  de  la  ville  connaissaient  le  chemin  de  sa  porte." 

(Madame  Duclaux.) 


ANNOTATED    LIST   OF   PERSONS  333 

Feltz,  Victor  Timothêe  (1835-1893).  French  pathologist.  Associated 
with  Coze. 

Fernbach,  Ernst  (— — ).     French  pathologist  at  the   Pasteur 

Institute. 

Fracastoro,  Girolamo  (1483-1553).  Italian  physician  and  poet. 
Famous  for  his  learning.  Born  in  Verona.  Wrote  in  verse 
"Syphilis,  sive  morbus  Gallicus"  (1530).  This  is  said  to  be  the 
first  use  of  the  word  syphilis.     For  portrait  see  Garrison,  p.  219. 

Fraenkel,  Albert  (1848 ).     German  physician,  bacteriologist  and 

pathologist.     Discovered    the    pneumococcus.     For    portrait    see 
Pagel,  p.  535. 

France,  Anatole,  pseudonym  of  Jacques  Anatole  Thibault  (1844 ). 

Greatest  of  living  French  stylists.     Author  of  many  books  and 
papers,  the  most  interesting  of  which,  perhaps,  are  certain  stories 
about  children,   and   four  volumes   of  literary   criticism   entitled 
"La  vie  littéraire."     A  master  of  irony.     It  was  he  who  said  of 
Zola's  novel  "La  Rêve:"  "I  marvel  it  can  be  so  heavy,  being  so 
flat!"     For  portraits  see  "Les  Annales,"  No.  1729.     Aug.  13,  1916. 
Frêmy,     Edmond     (1814-1894).     French    chemist.     Member    of    the 
Academy  of  Sciences.     Wrote  with  Pelouze  a  "Traité  de  chimie 
générale"    (7  vols.).     Editor  of  the   "Encyclopédie  de   Chimie," 
(11  vols.). 
Frey,    Heinrich     (1822-1890).      German    anatomist     and     zoologist 
Professor  in  Zurich.     Collaborated  with  Leuckart.     Published  a 
book  on  the  microscope  which  passed  through  many  editions,  and  a 
book  on  the  elements  of  histology  which  had  several  editions. 
Gay-Lussac,  Joseph  Louis  (1778-1850).     French  physicist  and  chemist. 
Member  of  the  Academy  of  Sciences.     Peer  of  France.     An  elevated, 
simple,  disinterested,  ingenious  and  philosophic  mind.     Discovered 
the  law  of  expansion  of  gases  known  as  Gay-Lussac's  law,  also  various 
other  laws.    In  1804  made  two  balloon  ascensions.     First  prepared 
with  Thénard  the  alkali  metals,  sodium  and  potassium,  in  quantity 
from  their  salts.     Also  with  Thénard  showed  chlorine  to  be  a  simple 
substance.     Developed  alkalimetry  and  acidimetry.     A  friend  and 
companion  of  Humboldt,   who  styled  him   (1850):  "ce  grand  et 
beau  charactère."     At  16  he  was  without  knowledge  of  the  sciences. 
He  learned  mathematics  without  a  teacher  and  tutored  his   way 
through  college,   studying  at  night.     For  portraits  see     Harper's 
Mag.,  1897,  p.  757,  and  Werckmeister,  1899,  v.  2,  pi.  214. 

Gernez,  Désiré  Jean  Baptiste  (1834 ).     French  chemist.     Student 

at  the  Normal  School.  Assisted  Pasteur  in  the  study  of  wines  and 
of  silkworm  diseases.  Officer  of  the  Legion  of  Honor.  Member  of 
the  Academy  of  Sciences.  Professor  in  the  Normal  School  (1898- 
1904).     Author  of  "Crystallization  of  supersaturated  solutions,"  etc. 


334  ANNOTATED    LIST   OP   PERSONS 

Gibier,  Paul  (1851-1900).     French  pathologist. 

Grancher,  Jacques  Joseph  (1843-1907).  French  physician.  Professor 
in  the  Faculty  of  Medicine.  Member  of  the  Academy  of  Medicine. 
Collaborated  with  Vulpian  in  vaccinating  men  for  prevention  of 
rabies.  Wrote  on  rabies,  tuberculosis  and  pneumonia.  One  of 
the  Editors  of  "Ann.  de  1'Inst.  Pasteur." 

Guérin,  Alphonse  François  Marie  (1817-1895).  French  surgeon. 
Member  of  the  Academy  of  Medicine  and  Commander  of  the  Legion 
of  Honor.  An  introducer  of  antiseptic  methods  into  French  surgery 
(after  the  war  of  1870). 

Guérin,  Jules  Rene  (1801-1886).  French  physician.  Editor  of  the 
"Gazette  médicale  de  Paris."  Founded  an  orthopaedic  institute. 
Opponent  of  the  preceding.  Challenged  Pasteur  to  a  duel  as 
result  of  a  dispute  over  vaccines. 

Guérin-Mène ville,  Félix  Edouard  (1799-1874).  French  zoologist  and 
entomologist.  Born  in  Toulon,  died  in  Paris.  Wrote  a  "Guide  to 
silkworm  culture"  (1856). 

Guy  on,  Casmir  Jean  Félix  (1831 ).     French  physician  and  surgeon- 

Following  Pasteur,  early  to  apply  antiseptics  to  diseases  of  the 
bladder  and  urethra.  Commander  of  the  Legion  of  Honor,  Pro- 
fessor in  the  Faculty  of  Medicine.  Member  of  the  Academy  of 
Medicine,  etc.  Author  of  an  atlas  of  a  hundred  plates  on  urinary 
diseases  (1881-1885).     For  portrait  see  Pagel,  p.  667. 

Hales,  Stephen  (1677-1761).  English  botanist,  physicist  and  inventor. 
Wrote  "Statical  Essays"  (1727)  and  "Haemastatics"  (1733). 
One  of  the  founders  of  scientific  physiology.  For  portraits  see 
Garrison,  p.  317,  and  Wittrock  II,  Tafl.  22. 

Hallier,  Ernst  (1831-1904).  German  botanist.  Assistant  to  Schleiden, 
Professor  in  Jena.  Author  of  many  books.  Quarreled  with  De 
Bary.  Much  of  his  scientific  work  was  vitiated  by  his  ideas  on 
species  transmutation.  Unable  to  reason  correctly  from  premises. 
Wrote  on  philosophy  and  aesthetics  toward  the  end  of  his  life. 

Hameau,  Jean  (1779-1851).  French  physician  of  La  Teste,  with  ideas 
somewhat  like  Henle's.  Author  of  "Étude  sur  les  virus."  For  por- 
trait see  "Arch.  d.  Parasit.,"  T.  2,  p.  317. 

Haûy,  René -Just  (1743-1822).  French  mineralogist.  Member  of  the 
Institute.  Founder  of  crystallography.  His  "Essai  d'une  théorie 
sur  la  structure  des  cristaux"  was  published  in  1784.  Brother  of 
Valentine  Haûy  who  invented  raised  characters  for  the  blind. 

Helmholtz,  Hermann  Ludwig  Ferdinand  von  (1821-1894).  German 
physicist,  anatomist  and  physiologist.  Published  on  conservation 
of  energy  (1847),  optics,  electricity  and  acoustics.  Professor  in 
Koenigsberg,    Bonn,    Heidelberg,    and    Berlin.     President    of    the 


ANNOTATED    LIST   OF   PERSONS  335 

Pysikalisch-Technischen  Reichsanstalt  in  Berlin.  His  chief  works 
are  on  optics  and  acoustics.  Invented  the  ophthalmoscope  (1850). 
It  was  he  who  said  :  "  The  only  laws  I  know  are  the  laws  of  physics." 
For  portraits  see  Garrison,  p.  562,  and  Pagel,  p.  714. 

Helmont,  Jean  Baptiste  van  (1577-1644).  Belgian  physician  and  mystic. 
Invented  a  system  of  medicine  founded  on  that  of  Paracelsus. 
Discovered  the  gastric  juice,  laudanum,  carbon  dioxide  (gas  syl- 
vestre) and  carbonate  of  ammonia.  Introduced  the  words  "gas" 
and  "ferment"  into  chemistry.  For  portrait  see  Garrison,  p. 
251. 

Henle,  Friederich  Gustav  Jakob  (1809-1885).  German  anatomist, 
physiologist  and  pathologist.  Professor  in  Zurich,  Heidelberg  and 
Gôttingen.  Published  important  books  and  papers  on  anatomy, 
physiology,  pathology,  zoology  and  anthropology.  His  paper 
referred  to  in  the  text  is  his  "  Pathologischen  Untersuchungen  " 
(1840).  See  also  his  "Handbuch  der  rationellen  Pathologie" 
(1853).     For  portraits  see  Garrison,  p.  473,  and  Pagel,  p.  718. 

Herschel,  Sir  John  Frederick  William  (1792-1871).  English  astronomer. 
Son  of  the  astronomer  Frederick  William  Herschel.  Famous  for 
his  catalogues  and  measurements  of  double  stars.  For  portraits 
see  "Tennyson  and  his  friends"  by  Cameron,  1893,  pi.  10,  and 
Harper's  Mag.,  1897,  p.  549. 

Hippocrates  (B.  C.  460 -).     Greek  physician  and  surgeon.    "The 

father  of  Medicine."  Descended,  so  said,  from  Aesculapius. 
Born  in  Cos.  Pupil  of  Democritus.  A  careful  observer  and  great 
clinician.  He  emancipated  medicine  from  many  superstitions  and 
enjoyed  a  great  reputation  as  a  healer,  not  only  during  his  life  but 
for  centuries  after.     For  portrait  from  a  bust  see  Garrison,  p.  81.  - 

Hoff  (See  Van-t-Hoff). 

Hoffmann,  Hermann  ( ■).     German  mycologist.     The  person 

referred  to  in  the  text  is  probably  the  above,  who  was  professor 
in  Giessen  in  1874. 

Hugo,  Victor  (1802-1885).  French  poet.  Son  of  Gen.  Hugo.  Born 
at  Besançon.  Member  of  the  French  Academy.  Peer  of  France. 
Spent  20  years  in  exile.  Great  lyric,  epic,  and  dramatic  poet. 
Copious  writer  of  romances  and  various  critical  and  philosophical 
essays.  Democratic  in  politics.  His  published  works  comprise 
eighty-two  volumes.  For  portraits  and  caricatures  see  Abry,  497, 
500,  502,  536,  540,  543. 

Jaillard,  Pierre  François  (1827-1883).  French  physician.  Professor  in 
Val  de  Grâce.     Associated  with  Leplat  in  anthrax  studies. 

Jenner,  Edward  (1749-1823).  English  physician.  Discovered  cowpox 
vaccine,  a  preventive  of  smallpox.  His  studies  of  it  were  begun 
in  1775  and  the  first  human  vaccination  was  in  1796.     His  first  book, 


336  ANNOTATED    LIST   OF   PERSONS 

with  illustrations,  "An  Inquiry  into  the  Causes  and  Effects  of 
Cowpox,  or  Variolar  Vaccina?,"  was  published  in  London  in  1798. 
For  portraits  see  Garrison,  p.  375,  and  Pagel,  p.  24. 

Joly,  Nicolas  (1812-1885).  French  physician  and  zoologist.  Professor 
of  physiology  in  Toulouse.  Member  of  the  Legion  of  Honor. 
Wrote  on  silkworms  and  their  diseases,  milk,  yeast  of  beer,  man 
before  metals,  comparative  psychology,  German  grammar  simplified, 
etc.     Antagonist  of  Pasteur. 

Joubert,  Jules  François   (1834 ■ — ■).     French  physicist,   especially 

interested  in  electricity,  on  which  he  published  two  books.  Pro- 
fessor at  Collège  Rollin.  One  of  Pasteur's  collaborators.  Officer 
of  the  Legion  of  Honor.  Ex-president,  Soc.  de  Physique,  and  of 
Soc.  d'Électriciens. 

Klebs,  Edwin  (1834-1913).  German  physician  and  pathologist. 
Virchow's  assistant.  Assistant  or  professor  in  various  places: 
Koenigsberg,  Bern,  Wurzburg,  Prague,  Zurich,  Asheville,  N.  C, 
Chicago  (Rush  Medical  College)  and  elsewhere.  For  portrait  see 
Garrison,  p.  614. 

Koch,  Robert  (1843-1910).  German  pathologist  and  bacteriologist. 
Geheimrat  Regierungsrat,  Med.  rat.  Born  at  Klausthal  in  the 
Harz.  A  great  investigator.  Studied  wound  infections  and  demon- 
strated their  aetiology  (1878).  Introduced  the  poured-plate  method 
(1881).  Discovered  the  cause  of  tuberculosis  (1882)  and  of  cholera 
(1884).  For  the  latter  discovery  he  was  given  100,000  marks  by 
the  German  Government.  Introduced  tuberculin  (1890).  In  1891 
was  made  director  of  the  newly  founded  Institute  for  Infectious 
Diseases  in  Berlin.  In  1896  discovered  a  remedy  for  rinderpest 
in  South  Africa.  Studied  malaria,  sleeping  sickness  and  other 
diseases  in  South  Africa,  which  he  visited  three  times.  Also  studied 
diseases  of  men  and  animals  in  India.  Visited  the  United  States 
in  1908.  For  portraits  see  Garrison,  p.  612,  Pagel,  p.  878,  and  Pop. 
Sci.  Monthly,  Dec,  1889. 

Kiitzing,  Friederich  Traugott  (1807-1893).  German  algologist.  Author 
of  "Synopsis  Diatomearum"  (1833);  "Tabulée  phycologicae " 
(1845-1870,  2  vols.,  2,000  colored  plates);  "Phycologia  generalis" 
(1843);  etc.  Distributed  exicatti  of  fresh  water  alga?  (16  parts). 
For  portrait  see  Wittrock  II,  Tafl.  64. 

Lackerbauer,  P.  ( — — ■ ■ — ).  Painter  and  photographer  who  illus- 
trated Pasteur's  book  on  diseases  of  silkworms. 

Lannelongue,  Odilon  Marc  (1840-1911).  French  surgeon  and  patholo- 
gist. Commander  of  the  Legion  of  Honor.  Professor  in  University 
of  Paris.  Senator.  Wrote  various  medical  papers,  also  "Travels 
Around  the  World."  Friend  of  Gambetta.  His  pathological  collec- 
tions are  in  the  Musée  Dupuytren.     For  portrait  see  Pagel,  p.  959. 


ANNOTATED   LIST   OF   PERSONS  337 

Lavoisier,  Antoine  Laurent  (1743-1794).  French  chemist  and  physicist. 
Member  of  the  Academy  of  Sciences.  One  of  the  greatest  investi- 
gators of  the  18th  century.  Founder  in  chief  of  modern  chemistry. 
He  created  chemical  nomenclature,  determined  the  composition 
of  air  and  water,  determined  the  rôle  of  oxygen  in  respiration 
and  combustion,  and  showed  that  the  diamond  is  a  form  of  carbon. 
"Nothing  can  be  destroyed,  nothing  can  be  created"  was  one  of  his 
favorite  expressions.  He  was  guillotined  during  the  French  Revo- 
lution. For  portraits  see  Garrison,  p.  325,  and  Pop.  Sci.  Monthly, 
Aug.,  1889. 

Le  Bel,   Joseph  Achille    (1847 ).     French   chemist.     Wrote  on 

stereochemistry. 

Lebert,  Hermann  (1813-1878).  German  physician,  pathologist,  chemist 
and  microscopist.  Author  of  numerous  memoirs  in  German  and 
French.  Studied  and  collected  with  Robin  in  France.  Professor 
in  Zurich  and  Breslau.  Wrote  on  various  pathological  subjects, 
including  pébrine  and  cancer. 

Lechartier,  Georges  Vital  (1837 ).     French  chemist.     Normalien. 

Student  of  Sainte-Claire-Deville.  Wrote  on  the  soy  bean  (Ann. 
Sci.  Agron.,  Paris,  1903). 

Leeuwenhoek,  Antony  van  (1632-1723).  Dutch  microscopist.  Some- 
times called  "The  father  of  microscopy."  Was  elected  member 
of  the  Royal  Society  of  London  and  of  the  Academy  of  Sciences 
of  Paris.  Discovered  infusoria,  bacteria,  spermatozoa,  striped 
muscle  fibers,  the  capillary  circulation  and  "globules"  in  the  blood. 
He  also  discovered  spiral  vessels  and  pitted  vessels  in  plants  and 
distinguished  between  the  structure  of  dicotyledonous  and  mono- 
cotyledonous  stems.  A  man  of  limited  education  but  great  per- 
sistency. The  first  opponent  of  spontaneous  generation.  His 
progenitors  were  wealthy  brewers.  For  portraits  see  Garrison,  p. 
243,  and  Pop.  Sci.  Monthly,  April,  1901. 

Lefèvre,  Amédêe  (1798-1869).     French  physician  and  chemist. 

Lémery,  Louis  (1677-1743).     French  chemist. 

Lémery,  "The  Younger"  ( 1721).     French  chemist.     Brother  of 

above.     One  of  these  is  probably  the  person  mentioned  in  the  text. 

Leplat,  F.  ( ).     French  student  of  anthrax  with  Jaillaird. 

Liebig,  Justus  von  (1803-1873).  German  organic  and  agricultural 
chemist.  An  industrious  analyst,  a  copious  writer,  and  a  competent 
teacher,  who  attracted  students  from  all  parts  of  Europe.  He 
organized  the  first  chemical  laboratory  for  students.  Studied 
with  Thénard  and  Gay-Lussac  in  Paris.  Professor  in  Giesseu 
and  Munich.  Discovered  chloroform,  chloral,  aldehyd,  hippuric 
acid,   tyrosin   and   many   other  substances.     Introduced   a  meat 

22 


338  ANNOTATED    LIST   OF   PERSONS 

extract  which  bears  his  name.  A  friend  of  Wôhler  with  whom 
he  edited  "Annalen  der  Chemie  und  Pharmacie."  Nearly  all  of 
his  ideas  on  biological  problems  have  now  been  set  aside.  For 
portraits  see  Garrison,  p.  492,  and  Pop.  Sci.  Monthly,  June,  1873. 

"As  to  the  opinion  which  explains  putrefaction  of  animal  sub- 
stances by  the  presence  of  microscopic  animalculse,  it  may  be 
compared  to  that  of  a  child  who  would  explain  the  rapidity  of  the 
Rhine  by  attributing  it  to  the  violent  movement  of  the  numerous 
mill-wheels  of  Mayence."     (Liebig,  1845.) 

Linnaeus  or  Linné,  Charles  de  (1707-1778).  Swedish  naturalist. 
Foreign  member  of  the  French  Academy  of  Sciences.  Knight  of 
the  Polar  Star.  Author  of  the  Linnean  system  of  botany,  founded 
on  the  reproductive  organs.  He  introduced  the  binary  system  of 
nomenclature,  and  described  many  genera  and  species.  A  copious 
writer  and  diligent  collector  of  plants  from  many  lands.  He  wrote 
among  other  things:  "Flora  Suecica,"  "Hortus  Upsaliensis," 
"Sy sterna  Naturae,"  "Fundamenta  Botanica,"  Genera  Plantarum," 
"Bibliotheca  Botanica,"  Critica  Botanica,"  "Classes  Plantarum," 
"Philosophia  Botanica,"  and  "Species  Plantarum"  (1753).  For 
portraits  see  Wittrock  I,  Tafl.  2,  2a,  26,  2c,  3,  3*  3**,  Wittrock  II, 
Tan.  25,  Garrison,  p.  304,  and  Pop.  Sci.  Monthly,  Oct.,  1899. 

Lister,  Joseph  (1827-1912).  Distinguished  English  surgeon.  Knighted, 
and  President  of  the  Royal  Society.  Son  of  a  distinguished  father. 
Professor  in  Edinburgh  and  King's  College  in  London.  The  first 
to  reform  surgical  operations  with  reference  to  bacterial  infections. 
He  treated  wounds  with  concentrated  phenol  and  operated  under 
a  phenol  spray.  He  banished  hospital  gangrene  and  from  his  work 
at  Glasgow  (1860-69)  dates  the  beginning  of  modern  surgery. 
Previous  to  his  improvements,  which  were  stimulated  by  Pasteur's 
discoveries,  the  healing  of  wounds  by  first  intention  was  a  rare 
occurrence  and  suppuration  and  septic  poisoning  raged  in  the 
surgical  wards  of  hospitals  like  the  plague.  For  portraits  see 
Minerva  XX,  Garrison,  p.  622,  Pagel,  p.  1019,  and  Pop.  Sci. 
Monthly,  March,  1898. 

Lôffler,  Friedrich  August  Johannes  (1852-1915).  German  physician, 
bacteriologist,  sanitarian,  and  pathologist.  Son  of  Gottfried 
Friedrich  Franz  Lôffler,  a  distinguished  army  physician.  Robert 
Koch's  pupil.  Professor  in  Greifswald.  Member  of  the  Imperial 
Board  of  Health.  Discovered  with  Schiitz  (1882)  the  cause  of 
glanders;  isolated  in  1884  the  cause  of  diphtheria  (Klebs  had  seen 
it  in  the  diphtheritic  membranes  in  1883);  in  1885  stained  the  organ- 
om  causing  erysipelas  of  the  pig,  and  furnished  the  first  full  account 
f  it.  (It  was  discovered  by  Pasteur  and  Thuillier.)  With  Frosch 
discovered   the  first   filterable  virus    (Foot   and    Mouth   disease). 


ANNOTATED    LIST   OF   PEKSONS  339 

With  Uhlworm  and  Leuckart  founded  the  "  Centralblatt  fiir  Bakteri- 
ologie  und  Parasitenkunde"  (1887).  For  portrait  see  Pagel,  p. 
1034. 

Loir,  Adrien  ( ).     Pasteur's  nephew.     Assistant  at  the  Pasteur 

Institute.     Director  of  the  Pasteur  Institute  in  Tunis. 

Ludwig,  Karl  Friederich  Wilhelm  (1816-1895).  German  physiologist 
of  same  group  as  Briicke,  Helmholtz  and  Du  Bois-Reymond.  Pro- 
fessor in  Zurich,  Marburg,  Vienna  and  Leipzig.  A  very  genial, 
upright,  lovable  man  and  a  great  teacher.  About  200  physiologists 
studied  in  his  laboratories.  Invented  the  kymograph.  For 
portraits  see  Garrison,  pp.  589  and  592,  and  Pagel,  p.  1055. 

Metchnikoff,  Elie  (1845-1916).  Russian  zoologist  and  pathologist. 
Professor  in  Odessa.  Resident  many  years  in  Paris.  Member  of 
the  French  Academy  of  Medicine  and  of  the  Royal  Society  of 
London.  Became  vice-director  of  the  Pasteur  Institute.  Dis- 
covered phagocytosis.  Wrote  a  book  on  "Immunity,"  another 
on  "Prolongation  of  Human  Life,"  and  a  third  on  "Old  Age." 
For  portraits  see  Garrison,  p.  619,  and  Critic,  1903,  p.  391. 

Mill,  James  (1773-1836).  English  economist.  Father  of  John  Stuart 
Mill. 

Mitscherlich,  Eilhard  (1794-1863).  German  physicist  and  chemist. 
Professor  in  Berlin.  Discovered  at  25  the  law  of  isomorphism 
(1819),  for  which  he  received  a  gold  medal  from  the  Royal  Society 
of  London.  Determined  dimorphism.  Described  the  paratar- 
trates.  Discovered  benzol,  nitrobenzol,  etc.  Interested  also  in 
geology.     For  portrait  see  Werckmeister,  1898,  v.  1,  pi.  100. 

"Un  jour,  dans  la  biblothèque  de  l'Ecole,  je  lus  une  note  du 
célèbre  chimiste  cristallographe  Mitscherlich,  relative  à  deux  combi- 
naisons salines  :  le  tartrate  et  le  paratartrate  de  soude  et  d'ammo- 
niaque. Après  en  avoir  étudié  toutes  les  propriétés,  Mitscherlich 
concluait  ainsi:  'La  nature  et  le  nombre  des  atomes,  leur  arrange- 
ment et  leurs  distances  sont  les  mêmes.  Cependant  le  tartrate 
dévie  le  plan  de  la  lumière  polarisée  et  le  paratartrate  est  indifférent.' 
Cette  note  restait  comme  un  point  d'interrogation  obstinément 
placé  devant  mon  esprit.  Comment  deux  substances  pouvaient- 
elles  être  aussi  semblables  sans  être  tout  à  fait  identiques?  Des 
mois  et  des  mois  se  passèrent.  Je  fus  reçu  agrégé  des  sciences 
physiques.  Cette  note  de  Mitscherlich  me  poursuivait  toujours. 
Par  une  série  d'expériences  dont  il  est  facile  de  retrouver  les  commen- 
taires explicatifs  dans  les  comptes  rendus  de  l'Académie  des  sciences, 
j'arrivai  à  séparer  le  paratartrate  de  soude  et  d'ammoniaque  en 
deux  sels  de  dissymétrie  inverse  et  d'action  inverse  sur  le  plan  de 
polarisation  de  la  lumière.  Coup  sur  coup  les  obscurités  de  la  note 
de  Mitscherlich  se  dissipèrent;  la  composition  et  la  nature  de  l'acide 


340  ANNOTATED   LIST   OF   PERSONS 

paratartrique  furent  expliquées;  une  grande  lueur  se  projeta  sur 
la  constitution  intime  des  corps,  puisque  les  principes  essentiels  à 
la  vie  m'apparaissaient  comme  devant  prendre  naisssance  sous 
l'influence  de  forces  dissymétriques.  Ce  premier  chapitre  de  phy- 
sique et  de  chimie  moléculaires  devait  me  conduire  à  d'autres 
chapitres  utiles  à  l'histoire  de  la  science.  Quelles  joies  de  travail 
j'ai  ressenties  pendant  ces  premières  années  de  recherches!"  (Pasteur 
in  1895.) 

Moitrel  d'Élément  (1678-1730).  French  physicist.  Discovered  a  means 
of  collecting  and  studying  gases.  Lived  in  great  poverty  and  was 
considered  "mad"  by  his  contemporaries.     Died  in  America. 

Molière  (Stage  name  of  Jean  Baptiste  Poquelin)  (1622-1673).  French 
actor  and  dramatist.  He  often  satirized  medical  men:  "Ils  savent 
la  plupart  de  fort  belles  humanités,  savent  parler  en  beau  latin; 
savent  nommer  en  grec  toutes  les  maladies,  les  définir  et  les  diviser; 
mais  pour  ce  qui  est  de  les  guérir,  c'est  ce  qu'ils  ne  savent  point 
du  tout."     (Le  Malade  imaginaire.) 

"On  me  vient  chercher  de  tous  les  côtés;  et,  si  les  choses  vont  tou- 
jours de  même,  je  suis  d'avis  de  m'en  tenir  toute  ma  vie  à  la  medicine. 
Je  trouve  que  c'est  le  métier  le  meilleur  de  tous;  car,  soit  qu'on 
fasse  bien,  ou  soit  qu'on  fasse  mal,  on  est  toujours  payé  de  même 
sort.  .  .  .  Un  cordonnier,  en  faisant  de  souliers,  ne  sauroit  gâter 
un  morceau  de  cuir,  qu'il  n'en  paye  les  pots  cassés;  mais  ici  l'on  peut 
gâter  un  homme  sans  qu'il  en  coûte  rien.  .  .  .  c'est  toujours  la 
faute  de  celui  qui  meurt."     (Le  Médecin  malgré  lui.) 

"Molière  is  the  greatest  French  poet,  he  is  so  Bane"  (Alfred 
Tennyson).  For  portraits  see  Petit  Larousse,  p.  1467,  Oeuvres 
complètes  de  Molière,  Lahure,  Paris,  1858,  p.  8,  and  Abry,  p. 
231. 

Montaigne,  Michel  Eyquem  de  (1533-1592).  French  essayist,  philoso- 
pher and  moralist.  Hardheaded,  always  demanding  a  reason,  satu- 
rated with  medieval  and  classical  learning  which  bristles  on  every 
page,  yet  kindly  and  interesting  beyond  most  ancient  writers,  he 
fills  a  place  in  literature  occupied  by  no  other  person.  For  por- 
traits see  Abry,  p.  105,  and  "Essais  de  Michel  Montaigne  avec  des 
notes  de  tous  les  commentateurs.  Edition  revue  sur  les  textes 
originaux."  Paris,  Firmin  Didot  Frères,  Fils  et  Cie.,  Libraires. 
1870. 

"So  long  as  an  unaffected  style  and  an  appearance  of  the  utmost 
simplicity  and  good  nature  shall  charm,  so  long  as  the  lovers  of 
desultory  and  cheerful  conversation  shall  be  more  numerous  than 
those  who  prefer  a  lecture  or  a  sermon,  so  long  as  reading  is 
sought  by  the  many  as  an  amusement  in  idleness,  or  a  resource  in 
pain,  so  long  will  Montaigne  be  among  the  favorite  authors  of 
mankind." — (Hallam). 


ANNOTATED   LIST.  OP   PERSONS  341 

"Il  faisait  trop   d'histoires,  parlait  trop  de  soi.     ...     le  sot 
projet  qu'il  a  de  se  peindre."     (Pascal.) 

Mûntz,  Charles  Achille  (1846-1917).  French  agronomist.  Member 
of  the  Academy  of  Sciences,  Officer  of  the  Legion  of  Honor.  Director 
of  the  Laboratories  of  the  National  Agronomic  Institute. 

Musset,  Charles  ( ).     Student  of  Joly  in  Toulouse. 

Nageli,  Karl  Wilhelm  von  (1817-1891).  Brilliant  Swiss-German  bota- 
nist. Born  near  Zurich.  Died  in  Munich.  Studied  in  Zurich, 
Genoa,  and  Berlin.  Professor  in  Freiburg,  Zurich  and  Munich. 
Systematist  of  higher  plants,  morphologist,  physiologist,  algologist, 
bacteriologist,  student  of  evolution.  His  discovery  of  wild  Hiera- 
cium  hybrids  and  of  oligodynamic  phenomena  (effect  of  very  dilute 
poisons)  in  living  cells  are  perhaps  his  best  known  work.  He  had 
a  habit  of  tasting  his  bacteriological  cultures  which  enabled  him  to 
make  many  fine  discriminations  but  undoubtedly  shortened  his 
life  (Oscar  Loew).  Wrote  with  Schwendener  Das  Mikroskop," 
2  ed.  1877.  For  a  list  of  his  books  see  Meyer's  "  Grosses  Konversa- 
tions-Lexikon,"  Leipzig,  1909.  For  a  portrait  see  Wittrock  II, 
Tan.  75. 

Needham,  John  Turberville  (1713-1781).  English  Jesuit,  physicist 
and  microscopist.  Member  of  the  Royal  Society.  Founded  the 
Academy  of  Sciences  in  Brussels  and  was  its  director.  Wrote 
"Microscopical  Discoveries"  (1745)  and  "Idée  sommaire,  ou  vue 
générale  du  système  physique  et  métaphysique  sur  la  génération" 
(1780).  Engaged  in  a  dispute  with  Voltaire  on  miracles.  Wrote 
a  book  to  show  that  the  Chinese  written  characters  indicate  descent 
from  the  Egyptians.  Walter  Needham,  with  whom  he  is  sometimes 
confused,  as  in  Garrison,  p.  318,  died  before  Spallanzani  was  born. 

Nocard,  Edmond  Isidore  Etienne  (1850-1903).  French  veterinarian. 
Professor  in  Alfort.  Member  of  the  Academy  of  Medicine.  Showed 
in  1880  that  the  cause  of  rabies  is  a  non-filterable  (solid)  virus. 
He  used  dog  saliva  and  filtered  it  through  plaster  of  Paris — what 
came  through  was  innocuous,  what  remained  on  the  filter  was 
infectious.  Wrote  on  tuberculosis,  glanders,  tetanus,  rabies, 
peripneumonia,  etc.  Author  with  Leclainche  of  "Les  maladies 
microbiennes  des  Animaux"  (3d  edition,  8  vo.,  2  volumes.  Paris, 
1905),  an  important  work  on  parasitic  diseases  of  domestic  animals. 
Was  on  the  Egyptian  cholera  commission  (1883).  Nocard  was  son 
of  a  wood  merchant.  For  a  portrait  see  Rec.  de  méd.  vét.  8  sér. 
Tome  X,  No.  15,  15  août,  1903. 

Noguchi,    Hideyo  (1876 ).     Distinguished  Japanese  pathologist 

working  in  the  United  States.  Obtained  Treponema  pallidum 
in  pure  culture.  Showed  connection  between  syphilis,  general 
paresis  and  locomotor  ataxia  by  finding  the  parasite  of   syphilis 


342  ANNOTATED    LIST   OF   PERSONS 

in  the  brain  and  cord.  Improved  syphilitic  diagnosis.  Cultivated 
the  rabies  parasite.  Cultivated  the  yellow  fever  parasite  (Lepto- 
spira icter aides  Nog.)  and  with  it  produced  the  disease  in  guinea 
pigs  ("Jour.  Exp.  Med.,"  vol.  29,  No.  6,  June  1,  1919). 

Obermeier,  Otto  Hugo  Franz  (1843-1873).  German  pathologist. 
Studied  the  spirillum  of  recurrent  fever  in  Berlin  in  1873.  His 
last  paper  was  "Die  ersten  Fâlle  und  der  charakter  der  Berliner 
Flecktyphusepidemie  von  1873  (Berl.  Klinische  Wochenschr.,  1873, 
X,  No.  30).  Died  of  cholera  while  studying  an  outbreak  of  this 
disease.    To  all  such  be  eternal  honor! 

Osimo,   Marco  ( ).     Italian  student  of  silkworm  diseases. 

Published  in  Padua  in  1859.  Recommended  eeg-selection  as  a 
remedy  for  pébrine. 

Paracelsus  (1493-1541).  German  Swiss  alchemist  and  physician. 
His  real  name  was  Theophrastus  Bombast  von  Hohenheim. 
Paracelsus  is  said  to  mean  superior  to  Celsus.  Learned,  original, 
obstinate  and  arrogant,  opposed  to  tradition,  a  great  traveler, 
a  shrewd  observer,  and  a  successful  healer,  he  died  in  poverty, 
destroyed  by  fools.  He  taught  the  doctrine  of  signatures  and  was 
hostile  to  Galen.  He  said:  "If  nature  can  instruct  irrational 
animals,  can  it  not  much  more  men?"  His  works  in  10  volumes 
were  published  in  Basel  in  1589-1591.  For  portraits  see  Garrison, 
p.  189,  and  Pagel,  p.  13. 

Pascal,  Blaise  (1623-1662).  French  mathematician,  physicist  and 
philosopher.  A  profound  thinker  and  great  prose  writer.  In- 
vented the  omnibus  and  the  calculating  machine;  made  important 
observations  with  the  barometer  in  high  places.  Wrote  "Lettres 
écrites  à  un  Provincial  par  un  de  ses  amis,"  a  covert  arraignment 
of  the  Jesuits,  in  which  he  is  "witty  as  Molière  and  eloquent  as 
Bossuet"  (Voltaire),  and  "Pensées  sur  la  religion."  A  deeply 
religious  Roman  Catholic,  he  abandoned  scientific  pursuits  in  1649 
for  religious  studies  and  became  very  ascetic.  For  portraits  see 
Lettres  Provincial,  Paris,  Firmin  Didot  Frères,  1846,  and,  Abry,  pp. 
200,  208  (masque). 

Pascal,    Etienne    ( ■)•     French  advocate.   President  of  the 

Court  of  Aids.     Father  of  Blaise  Pascal. 

Pasteur,  Louis  (1822-1895).  French  physicist,  chemist,  microscopist 
and  pathologist.  Son  of  a  tanner  whose  father  and  grandfather 
were  also  tanners.  A  man  with  an  iron  will  and  a  great  soul, 
born  for  combat  and  mastery.  Professor  in  Dijon,  Strasburg, 
Lille  and  Paris.  In  1874  the  French  Government  granted  him  a  life 
annuity  of  12,000  francs  in  consideration  of  his  public  services  and 
out  of  the  556  votes  there  were  only  24  dissenting  ones.  Nine 
years  later,  again  through  the  instrumentality  of  Paul  Bert,  this  was 


ANNOTATED   LIST   OF   PERSONS  343 

increased  to  25,000  francs.  Pasteur  succeeded  Littré  in  the 
Académie  Française.  Monuments  have  been  erected  to  him  in 
Melun,  Lille,  Arbois,  Dole,  Besançon  and  Paris.  Both  Roty  and 
Dubois  made  low  relief  circular  bronze  plaques  of  Pasteur.  That 
by  Dubois,  especially  the  larger  one  (7  inch),  is  very  desirable. 
There  is  also  a  fine  bust  by  Dubois  in  Copenhagen.  For  a  frank 
and  charming  letter  at  26,  proposing  marriage,  see  "Les  Annales," 
Paris,  2  Février,  1919,  p.  105,  and  for  a  vivid  description  of  his 
personal  appearance  at  the  time  of  his  rabies  studies,  see  "  Monsieur 
Taine  and  Monsieur  Pasteur"  by  Gabriel  Hanotaux  of  the  French 
Academy  (Ibid.,  pp.  102-103).  For  a  bibliography  of  his  principal 
writings  consult  "Revue  scientifique,"  4  se.,  tome  IV,  No.  14, 
Paris,  1895,  pp.  427-431.  For  portrait  as  a  young  man  see  "Les 
Annales,"   1.  c,  p.  105,  and  when  old,  Wittrock  II,  Tafl.  78. 

"At  the  middle  of  the  last  century  we  did  not  know  much  more  of 
the  actual  causes  of  the  great  scourges  of  the  race,  the  plagues, 
the  fevers  and  the  pestilences,  than  did  the  Greeks.  Here  comes  in 
Pasteur's  great  work.  Before  him  Egyptian  darkness;  with  his 
advent  a  light  that  brightens  more  and  more  as  the  years  give  us 
ever  fuller  knowledge.  *  *  *  It  was  a  study  of  the  processes  of 
fermentation  that  led  Pasteur  to  the  sure  ground  on  which  we  now 
stand."  (Sir  Wm.  Osier.) 

"Your  father  is  absorbed  in  his  thoughts,  talks  little,  sleeps  little, 
rises  at  dawn,  and,  in  one  word,  continues  the  life  I  began  with  him 
this  day  thirty-five  years  ago."     (Madame  Pasteur,  1884.) 

Aphorisms  and  Ideals  of  Pasteur  : 

The  characteristic  of  a  true  theory  is  its  fruitfulness. 

Science  should  not  concern  itself  in  any  way  with  the  philosophi- 
cal consequences  of  its  discoveries. 

Hypotheses  come  into  our  laboratories  in  armfuls,  they  fill  our 
registers  with  projected  experiments,  they  stimulate  us  to  research 
— and  that  is  all. 

The  recompense  and  the  ambition  of  a  scientist  is  to  conquer  the 
approbation  of  his  peers  and  of  the  masters  whom  he  venerates. 

It  would  seem  to  me  that  I  was  committing  a  theft  if  I  were  to 
let  one  day  go  by  without  doing  some  work. 

If  that  teaching  [the  higher  education]  is  but  for  a  small  number, 
it  is  with  this  small  number,  this  élite,  that  the  prosperity,  glory  and 
supremacy  of  a  nation  rest. 

Whatever  career  you  may  embrace,  look  up  to  an  exalted  goal;  wor- 
ship great  men  and  great  things.     [To  the  students  at  Edinburgh.] 

Great  is  the  joy  of  a  teacher  whose  pupils  become  masters. 

A  man  of  science  should  think  of  what  will  be  said  of  him  in 
the  following  century,  not  of  the  insults  or  the  compliments  of  one 
day. 


344  ANNOTATED   LIST   OP   PERSONS 

H  y  a  dans  la  jeunesse  de  tout  homme  de  science  et  sans  doute  de 
tout  homme  de  lettres,  un  jour  inoubliable  où  il  a  connu,  à  plein  esprit 
et  à  plein  coeur,  des  émotions  si  généreuses,  où  il  s'est  senti  vivre 
avec  un  tel  mélange  de  fierté  et  de  reconnaissance,  que  le  reste  de 
son  existence  en  est  éclairé  à  jamais.  Ce  jour-là,  c'est  le  jour  où  il 
s'approche  des  maîtres,  à  qui  il  doit  ses  premiers  enthousiasmes,  dont 
le  nom  n'a  cessé  de  lui  apparaître  dans  un  rayonnement  de  gloire. 
Voir  enfin  ces  allumeurs  d'âmes,  les  entendre,  leur  parler,  leur  vouer 
de  près,  a  côté  d'eux,  le  culte  secret  que  nous  leur  avions  si  longtemps 
gardé  dans  le  silence  de  notre  jeunesse  obscure,  nous  dire  leur  disciple 
et  ne  pas  nous  sentir  trop  indignes  de  l'être!  Ah!  quel  est  donc  le 
moment,  quelle  que  soit  la  fortune  de  notre  carrière,  qui  vaille 
ce  moment-là  et  qui  nous  laisse  des  émotions  aussi  profondes? 

Péligot,  Eugène  Melchoir  (1811-1890).  French  chemist.  A  student 
of  silkworms.  Pasteur's  associate.  Wrote  "Traité  de  chimie 
analytique  appliquée  à  l'agriculture"  (1883). 

Perdrix,  Charles  ( ).    French  pathologist.     Normal  school 

assistant. 

Pfeffer,  Wilhelm  (1845 ).     German  plant  physiologist.     Professor 

in  University  of  Leipzig.  Author  of  many  papers.  Discovered 
osmotic  pressure  in  plant  cells,  chemotaxis  of  bacteria,  etc.  His 
extensive  and  important  "  Physiology  of  Plants"  has  been  translated 
into  English  by  A.  J.  Ewart  (Oxford:  Clarendon  Press).  For  por- 
trait see  Wittrock  II,  Tafl.  94,  and  Pop.  Sci.  Monthly,  Jan.,  1897. 

Pfeiffer,  August   (1848 ).     German  physician,  bacteriologist  and 

pathologist.     This  man,  or  the  next,  must  be  the  one  named  in  the 

text. 
Pfeiffer,   Richard    (1858 ).     German    physician,    sanitarian  and 

bacteriologist.     Robt.    Koch's    assistant.     Professor    in    Breslau. 

Discoverer  of  the  influenza  bacillus.     Associated  with  Carl  Frânkel. 

Wrote  on  immunity.     For  portrait  see  Wittrock  II,  Tafl.  130. 

Philippi.  The  person  referred  to  in  the  text  under  this  name  is  Filippo 
de  Filippi  {1814-1867)  commonly  known  as  de  Philippi,  a  distin- 
guished naturalist  of  Turin  and  Milan.  At  one  time  he  was  Pro- 
fessor of  Zoology  in  the  University  of  Turin.  Afterwards  he  was 
Senator.  He  wrote:  Alcune  Osservazioni  Anatomico-Fisiologiche 
sugl'-Insetti  in  Générale,  ed  in  Particolare  sul  Bombice  del  Gelso." 
(Annali  della  Accad.  R.  d'  Agric.  di  Turino,  Vol.  V.,  1851,  pp.  1-25, 
3  plates). 

Piria,  Raffaele  (1815-1865).  Italian  chemist  and  patriot  (Garabaldian) ; 
senator.  Wrote  "Elements  of  Inorganic  Chemistry;"  "Lessons 
on  Fermentation;"  "Elements  of  Organic  Chemistry"  (2d  éd., 
Turin,  1870),  etc.  Hfe 


ANNOTATED    LIST   OP   PERSONS  345 

Pollender    ( -).     German    veterinarian.     His    paper    on    the 

microscopic  and  microchemical  investigation  of  anthrax  blood 
was  published  in  1855  in  Vierteljahrschr.  f.  ger.  Med.,  Bd.  8. 

Pouchet,  Felix  Archimede  (1800-1872).  French  naturalist.  Director 
of  the  Museum  of  Natural  History  in  Rouen.  Opponent  of  Pasteur. 
His  "Heterogenic,  ou  Traité  de  la  génération  spontanée,  etc." 
was  published  in  Paris  in  1859  (pp.  32,  672)  and  his  "L'Origine 
de  la  Vie"  (3d  éd.)  in  Paris  in  1868.  The  Maladetta  on  which 
Pouchet  opened  flasks  of  hay-infusion,  all  of  which  clouded,  is  a 
glaciated  mountain  in  the  Alps. 

Provostaye,  or  Hervé  de  la  Provostaye,  Frederick  (1812-1863).  French 
crystallographer. 

Quatrefages  de  Bréau,  Jean  Louis  Armand  de  (1810-1892).  French 
anatomist,  zoologist  and  anthropologist.  Member  of  the  Royal 
Society  of  London.  A  clear,  forcible,  fluent  writer.  He  wrote  a 
"Histoire  générale  des  races  humaines"  (1886-1889),  and  "La 
race  prussiene"  (1871)  which  led  to  a  polemic  with  Virchow.  For 
portrait  see  Pop.  Sci.  Monthly,  March,  1885. 

Quevenne,  Theodore  Auguste  (1805-1855). 

Rabenhorst,  Ludwig  (1806-1881).  German  botanist.  Author  of  a 
cryptogamic  Flora  of  Germany;  "Flora  Europsea  algarum,"  etc.; 
collected  and  distributed  dried  cryptogamic  plants.  Founded 
"Hedwigia." 

Raulin,   Jules  ( — .     French  chemist  and  physicist.     Student 

at  the  Normal  School.  Pasteur's  assistant.  Professor  in  Brest, 
Caen  and  Lyons.  His  famous  paper  "Études  chimiques  sur  la 
végétation"  is  in  Ann.  des  Sci.  Nat.  Bot.  V  sér.  Tome  XI,  Paris, 
1869,  pp.  93-299. 

Rayer,   Roger   J.    ( ).     French  physician  and   pathologist. 

Rayer's  account  of  the  discovery  of  the  rods  in  anthrax  blood  is  in 
"C.  R.  Soc.  biol.,"  1850,  p.  141. 

Recklinghausen,  Friedrich  Daniel  von  (1833-1910).  German  patho- 
logical anatomist.  Virchow's  student.  Assistant  in  Berlin. 
Professor  in  Kônigsberg,  Wûrzburg,  and  Strassburg.  Author  of  im- 
portant papers  on  inflammation,  the  lymphatic  system,  and  multiple 
fibromas.  Discovered  the  wandering  cells  of  the  connective  tissue 
and  the  ameboid  movements  of  living  pus  cells.  His  paper  on 
Erysipelas  is  in  Virchow's  Archiv,  Bd.  60,  1874.  For  portrait  see 
Pagel,  p.  1351. 

Redi,  Francesco  (1626-1698).  Italian  physician  and  naturalist.  Born 
in  Arezzo,  practiced  in  Florence.  Discovered  the  itch  mite.  Ap- 
plied the  experimental  method  in  natural  science.  He  was  also 
a  poet.     For  portrait  see  Garrison,  p.  245. 


346  ANNOTATED    LIST   OF   PERSONS 

Reess,  Max  Ferdinand  Friedrich  (1845-1901).  German  mycologist. 
Professor  in  Erlangen  and  director  of  the  botanic  garden. 
Produced  the  first  lichen  synthesis.  Published  "Rust  fungi  of  Ger- 
man Conifers"  (1869);  "Alcoholic  fermentation  fungi"  (1870); 
"Nature  of  Lichens"  (1879),  etc.  For  portrait  see  Wittrock  II, 
Tafl.  125. 

Renan,  Ernest  (1823-1892).  French  Semitic  scholar.  Born  in  Brittany. 
Member  of  the  French  Academy.  Director  of  the  College  of  France. 
One  of  the  most  engaging  and  delightful  writers  of  modern  France. 
Author  of  "Histoire  des  origines  du  Christianisme"  (8  vols.); 
"Histoire  du  peuple  d'Israël"  (5  vols.),  "Ma  Soeur  Henriette," 
"Souvenirs  d'enfance  et  de  jeunesse,"  and  many  other  books.  For 
portraits  see  Pop.  Sci.  Monthly,  April,  1893,  "Souvenirs  d'enfance 
etc."  (Nelson  ed.)  and  Abry,  p.  630. 

Rindfleisch,  Georg  Eduard  (1836-1908).  German  pathological  anato- 
mist. Assistant  to  Haidenhain.  Professor  in  Zurich,  Bonn  and 
Wurzburg.  Author  of  a  handbook  of  pathological  anatomy 
which  passed  through  many  editions.  For  portrait  see  Pagel,  p. 
1391. 

Rossignol,   H.    ( ■ ).     French  veterinary     surgeon  of  Melun. 

It  was  he  who  collected  by  subscription  money  for  the  famous 
anthrax  experiments  at  Pouilly-le-Fort. 

Roux,  Pierre  Paul  Emile  (1853 ).  French  physician,  bacteri- 
ologist and  pathologist.  Pupil  of  Duclaux.  Normal  School  as- 
sistant. Collaborated  with  Pasteur,  Chamberland,  etc.  Present 
director  of  the  Pasteur  Institute.  Dr.  Roux  has  made  important 
contributions  on  rabies,  diphtheria,  tetanus  and  other  diseases. 
His  studies  of  diphtheria  with  Yersin  preceded  and  laid  the  foundation 
for  those  of  Behring  and  Kitasato.  Diphtheritic  antitoxin  (serum) 
obtained  from  vaccinated  horses  was  used  by  Roux  in  1894  in  a 
Paris  hospital  on  hundreds  of  children  with  marvellous  results. 
For  portraits  see  "Bacteria  in  Relation  to  Plant  Diseases,"  vol. 
I.  Frontispiece.  Carnegie  Institution  of  Washington,  and  Mc- 
Clure's  Mag.,  1893,  p.  338. 

Saint-Simon,  Louis  de  Rouvray,  duc  de  (1675-1755).  Brilliant,  biting, 
picturesque  French  diarist,  especially  of  the  Court  of  Louis  XIV. 
A  great  painter  of  manners.  His  "Memoirs"  in  20  volumes  is  a 
vast  historical  storehouse.  For  portraits  see  Abry,  p.  296,  and 
Saint-Simon  "Mémoires  sur  le  Siècle  de  Louis  XIV,  et  la  Régence." 
Bibliothèque  Larousse,  Paris,  1911 — a  good  4  vol.  abridgement. 

"Nul  écrivain  démocratique  n'a  porté  comme  lui  le  fer  rouge 
dans  les  ulcères  de  la  noblesse."  (Larousse:  Grand  Diet,  universel 
du  XIXe  Siècle. 


ANNOTATED    LIST   OF   PERSONS  347 

Sainte-Claire-Deville,  Henri  Etienne  (1818-1881).  French  chemist. 
Brother  of  the  geologist.  Both  were  Students  at  Collège  Rollin. 
Professor  in  the  Normal  School  and  in  the  Sorbonne.  Member  of 
the  Academy  of  Sciences.  Discovered  high  temperature  disasso- 
ciation. Studied  the  silicates.  Improved  methods  of  working 
platinum,  aluminium,  sodium  and  magnesium.  Discovered  nitric 
anhydride  (1849).  Obtained  in  masses,  melted  and  pure,  the  re- 
fractory metals,  manganese,  chromium,  nickle  and  cobalt;  with 
Caron  succeeded  in  producing,  artificially,  rubies,  sapphires,  and  ori- 
ental emeralds.  Induced  the  Metric  Commission  to  use  an  alloy 
of  platinum-iridium  for  its  standards  and  during  the  last  ten  years 
of  his  life  was  engaged  with  his  illustrious  friend  Stas  of  Belgium  in 
preparing  sets  of  these  measures,  which  were  not  permitted  to  vary 
more  than  one  thousandth  of  a  millimeter.  Friend  of  Pasteur. 
Collaborated  with  Wohler,  Caron,  and  Debray.  For  portraits 
see  "Le  Centenaire  de  l'École  normale"  (1895),  p.  407,  and  Pop. 
Sci.  Monthly,  Feb.,  1882. 

For  a  splendid  appreciation  of  Sainte-Claire-Deville  by  Désiré 
Gernez  see  "Le  Centenaire  de  l'École  normale."  Paris,  1895. 
pp.  407-425. 

"H  est  impossible  de  décider  lequel  des  deux  fut  le  plus  grand 
en  lui,  de  l'homme  de  science  ou  de  l'homme  de  bien." 

"Puisse  son  example  développer,  chez  les  jeunes  gens  qui  s'en- 
gagent dans  la  carrière  scientifique,  le  dévouement  à  la  Science, 
l'une  des  formes  les  plus  élevées,  les  moins  bruyantes  et  les  plus 
pures  de  l'amour  de  la  Patrie!"     (Gernez.) 

Sanson,  ( ).     French  pathologist. 

Schroder,  H.  ( ).     German  chemist.     Collaborated  with  Th. 

von    Dusch   on   fermentation   and   also   published   independently. 
Wrote  many  papers  on  "Volumconstitution  fester  Kôrper." 

Schwann,  Theodore  (1810-1882).  German  physician  and  naturalist. 
Professor  in  Louvain  and  Liege.  Discovered  pepsin  in  gastric 
juice.  Following  Robert  Brown's  discovery  of  the  nucleus  in  plant 
cells  (1831)  and  Schleiden's  studies,  he  discovered  the  nucleus  in 
animal  cells,  and  showed  (1839)  that  animals  and  plants  are 
composed  of  the  same  (cellular)  elements  ("Mikroskopische  Unter- 
suchungen  iiber  die  Uebereinstimmung  in  der  Structur  und  dem 
Wachsthum  der  Thiere  und  Pflanzen,"  Berlin,  1839).  Schwann's 
observations  referred  to  in  the  text  were  published  in  1837  in  Pogg. 
Ann.  der  Physik  und  Chemie,  Bd.  XLI,  p.  184  ("Vorlâufige 
Mittheilung,  betreffend  Versuche  iiber  die  Weingàhrung  und 
Fàulniss"). 

Schulze,  Franz  ( ).     German  chemist  in  Berlin.     His  lucid  paper 

"Vorlâufige    Mittheilung    der    Resultate    Einer    Experimentellen 


348  ANNOTATED    LIST   OF   PERSONS 

Beobachtung  uber   Generatio   aequivoca,"   is  in   Pogg.     Annalen 
der  Physik  u.  Chemie,  Bd.  39,  Leipzig,  1836,  pp.  487-489. 

Schutzembach,  ( — — ■ ).     German  chemist. 

Sédillot,  Charles  Emmanuel  (1804-1883).  French  surgeon.  Born  in 
Alsace.  Served  in  the  war  of  1870  as  surgeon.  Introduced  the 
word  microbe  (C.  R.  de  l'Acad.  des  Sci.,  March  11,  1879).  The 
following  is  one  of  his  aphorisms:  "Le  succès  des  opérations  dépend 
de  l'habileté  du  chirurgien.  Le  revers  accusent  notre  ignorance 
ou  nos  fautes,  et  la  perfection  est  le  but  de  l'art." 

Sévigné,  Madame  Marquise  de,  née  Marie  de  Rabutin-Chantal  (1626- 
1696).  Parisian  of  the  time  of  Louis  XIV.  Greatest,  with  perhaps 
the  exception  of  Voltaire,  of  all  French  letter  writers.  For  a  por- 
trait see  Abry,  p.  189. 

"Sa  correspondence  est  un  tableau  fidèle  de  la  société  et  des  moeurs 
du  XVIIe  siècle;  c'est  un  journal  des  faits  les  plus  intéressant  des 
quarante  plus  belles  années  du  Siècle  de  Louis  XIV.  C'est  surtout 
un  des  monuments  de  la  literature  française." — (Larousse:  Grand 
Diet,  universel  du  XIXe  Siècle.) 

Signol,  Jean  Jules  (1841-1904).  French  veterinarian.  Signol's 
confusing  discovery  in  relation  to  anthrax  was  announced  in  1875. 

Spallanzani,  Lazzaro  (1729-1799).  Italian  physiologist,  naturalist,  abbé, 
and  traveler.  Educated  at  Bologna.  Professor  of  logic,  meta- 
physics and  Greek  in  Reggio  ;  then  of  natural  history,  first  in  Univer- 
sity of  Modena  (1760-1769),  afterward  in  University  of  Pavia. 
One  of  the  most  perspicacious  minds  of  the  18th  century.  It  is 
said  that  we  owe  to  him  our  first  exact  notions  of  circulation  of  the 
blood,  digestion,  respiration  and  generation  in  plants  and  animals. 
In  1785  he  fertilized  eggs  by  means  of  spermatozoa.  For 
portrait  see  Iconogr.  di  uomini  sommi  nelle  scienze  e  nelle  arti 
italiane.  Napoli,  Soc.  Editrice  (1854)  pi.  69. 

Stahl,  George  Ernst  (1660-1734).  German  chemist  and  physician. 
Opposed  Hoffmann  and  developed  a  doctrine  of  psychic  influence 
known  as  animism.  Professor  in  Halle.  Physician  to  the  King 
of  Prussia.  His  "Zymotechnica  fundamentalis  seu  fermentationis 
theoria  generalis"  was  published  at  Halle  in  1697.  For  portrait 
see  Pagel,  p.  18. 

Strauss,  Isidor  (1845 ■ — ).  French  physician  and  pathologist.  Pro- 
fessor of  comparative  and  experimental  pathology  in  Paris.  Co- 
operated with  Chamberland  in  studies  on  transmission  of  anthrax, 
and  with  Roux,  Nocard  and  Thuillier  on  cholera  in  Egypt.  Wrote 
on  cholera  in  Toulon  (1884),  etc.     For  portrait  see  Pagel,  p.  1670. 

Susani,  Guido  ( ).     Italian  silkworm  proprietor.     Published 

iia  several  papers  on  silkworms  in  Milan,  1870-72.  Entertained 
Pasteur. 


ANNOTATED    LIST   OF   PERSONS  349 

Talamon,  Charles  (1850 ).     French  physician  and  pathologist. 

Student  of  pneumococcus.     Discovered  it  independently  of  Frânkel. 

Tennyson,  Alfred  (1809-1892).  English  poet.  Laureate  and  knighted 
baronet.  Son  of  a  clergyman,  brother  of  two  other  poets,  Charles 
and  Frederick  T.  Born  at  Somersby,  in  Lincolnshire,  educated 
at  Trinity  College,  Cambridge.  Author  of  charming  lyrics,  elegies, 
odes,  epical  verse,  and  dramas.  The  most  distinguished  and  finished 
English  poet  of  the  19th  century  and  the  one  who  best  expressed  the 
prevalent  sentiment  of  scientific  and  social  unrest,  with  which  he 
mingled  a  deep  religious  strain.  He  lived  a  very  retired  life. 
"Smokes  infinite  tobacco"  (Carlyle).  For  portraits  see  Alfred 
Lord  Tennyson,  A  memoir  by  his  son  (the  original  2  vol.  ed.)  and 
Cameron's  "Tennyson  and  His  Friends." 

Thénardj  Louis  Jacques  de  (1777-1857).  French  chemist.  (See 
Gay-Lussac.)  Professor  in  the  College  of  France  and  in  the  Poly- 
technic School.  Discovered  cobalt  blue  (Thénard's  blue)  and 
hydrogen  peroxide.  With  Gay-Lussac  discovered  boron.  Dis- 
covered an  improved  way  of  making  white  lead.  A  great  and 
genial  teacher.  He  is  said  to  have  had  40,000  students.  His 
"Traité  de  chimie  élémentaire"  passed  through  six  editions  and 
was  translated  into  German.  Member  of  the  Institute  and  Peer 
of  France.  For  portrait  see  Arnault.  Biog.  Nouvelle  Contemp. 
1825,  19,  p.  424. 

Thomas,  Philippe  Etienne  (1843 — ■).     French  veterinarian. 

Thuillier,  Louis  Ferdinand  (1856-1883).  French  pathologist.  A 
student,  then  brilliant  associate  of  Pasteur.  Discovered  with 
Pasteur  the  cause  of  "rouget"  and  a  vaccine  for  it.  Collaborated 
on  anthrax  and  on  rabies.  Died  of  cholera  in  Egypt  where  he 
had  gone  to  study  a  violent  outbreak  of  the  disease. 

"C'était   une   nature   profondément  méditative  et  silencieuse," 
(Pasteur.) 

For  a  brief  account  of  Thuillier  by  Costantin  see  "Le  Centenaire 
de  l'École  normale,"  Paris,  1895,  pp.  540-543. 

There  is  in  the  Normal  School  a  bust  and  a  portrait  of  Thuillier 
and  a  marble  tablet  which  says:  "Thuillier,  mort  pour  la  science." 

Thuret,  Gustave  Adolphe  (1817-1875).  Distinguished  French  algologist. 
For  a  biographic  notice  and  a  list  of  his  publications  by  Ed.  Bornet 
see  Ann.  Sci.  Nat.  Bot.  6sé.,  Tome  II,  pp.  308-360.  For  portrait 
see  Wittrock  II,  Tan.  76. 

Tiegel,  Ernst  (1849 ■)•     Swiss  bacteriologist.     Associate  of  Klebs. 

Toussaint,  Jean  Joseph  Henri  (1847-1900).  French  veterinarian. 
Professor  in  the  school  at  Toulouse.  Toussaint's  report  to  the 
Minister  of  Agriculture  on  anthrax  is  in  "Archives  Vétérinaires," 
1879.      See  also  "C.  R.  d.  s.  de  l'Acad.  des  Sci.,"  1880,  p.  155. 


350  ANNOTATED    LIST   OF   PERSONS 

Trécul,  Auguste  Adolphe  Lucien  (1818-1896).  French  botanist.  Mem- 
ber of  the  Academy  of  Sciences  and  Chevalier  of  the  Legion  of 
Honor.  Made  botanical  collections  in  the  United  States  and  North 
Mexico.     Adversary  of  Pasteur. 

"  Heterogenesis  is  a  natural  operation  by  which  life,  on  the  point 
of  abandoning  an  organized  body,  concentrates  its  action  on  some 
particles  of  that  body  and  forms  thereof  beings  quite  different 
from  that  of  the  substance  which  has  been  borrowed"  (Trécul, 
1867). 

Turpin,  Pierre  Jean  Francois  (1775-1840).  French  artist  and  botanist- 
Wrote  "Iconographie  végétale"  (Paris,  1841).  Illustrated  Hum- 
boldt's works. 

Tyndall,  John  (1820-1893).  English  physicist.  Studied  under  Bunsen 
at  Marburg.  Professor  in  the  Royal  Institution  in  London.  Wrote 
with  Huxley,  and  independently,  on  glaciers  and  showed  their 
movement  to  be  due  to  fracture  and  refreezing.  Studied  heat, 
light,  sound  and  fermentation.  Discovered  intermittent  steriliza- 
tion. President  of  the  British  Association  for  the  Advancement 
of  Science  at  the  Belfast  meeting.  A  friend  of  Pasteur  and  op- 
ponent of  Bastian.  A  great  teacher  and  popularizer  of  modern 
science.  For  portraits  see  Pop.  Sci.  Monthly,  Nov.,  1872,  Harper's 
Mag.,  1888,  p.  831,  and  Critic,  1893,  p.  382. 

Van-t-Hoff,  Jacobus  Hendrikus  (1852-1911).  Dutch  chemist  and 
physicist.  Professor  in  Amsterdam  and  then  in  Berlin.  A  great 
stereo-chemist  and  one  of  the  founders  of  physical  chemistry. 
Born  in  Rotterdam.  In  1876  he  was  docent  in  physics  in  the  veteri- 
nary school  in  Utrecht,  hence  one  of  the  German  chemists,  who 
was  worsted  in  an  argument,  called  him  "horse  doctor."  For 
portraits  see  "Chemisch  Weekblad"  Amsterdam,  Oct.  15,  1910, 
and  Les  prix  Nobel  en  1901,  p.  76. 

Van  Tieghem,  Philippe  Edouard  Léon  (1839-1914).  French  botanist. 
Entered  the  Normal  School  in  1858.  Professor  in  the  Normal  School, 
in  the  Sorbonne  and  in  the  Museum  of  Natural  History.  Member  of 
the  Academy  of  Sciences  and  of  the  Legion  of  Honor.  Friend  of 
Pasteur.  Author  of  numerous  important  researches,  chiefly  anatom- 
ical and  morphological.  The  second  edition  of  his  important 
"Traité  de  Botanique"  (pp.  xxxi,  1855)  was  published  in  Paris  in 
1891.  Editor  of  "Ann.  des  Sci.  Nat.  Bot."  for  thirty-two  years. 
For  portrait  see  Ann.  des  Sci.  Nat.  Bot.,  Tome  XIX,  No.  1,  1914. 

Varro,  or  Varrone.  Roman  poet  and  prose  writer  of  the  Second  Century. 
Among  many  other  things  he  wrote  "Rerum  rusticarum." 

Vergnette-Lamotte,  Gérard  Alfred  Vicomte  de  (1806-1886). 


ANNOTATED    LIST   OF   PERSONS  351 

Viala,   Eugène   ( — ).     Assistant  in  rabies  vaccinations  at  the 

Pasteur  Institute.  A  boy  educated  by  Pasteur,  who  became  a 
devoted  and  skillful  assistant. 

Virchow,  Rudolph  (1821-1902).  Distinguished  German  physician, 
pathologist,  sanitarian,  anthropologist,  and  politician  (Prussian). 
Geheimrat,  Medicinalrat.  Professor  in  Wurzburg  and  in  Berlin. 
A  man  of  good  judgment,  broad  views  and  tremendous  energy. 
Founder  of  a  system  of  cellular  pathology,  which  has  had  great 
influence  on  modern  medicine.  His  book  "Cellular  Pathology" 
passed  through  four  editions.  A  copious  writer.  Founded  with 
Reinhardt  the  "Archiv  fur  pathologische  Anatomie  und  Physio- 
logic" Wrote  "The  Pathology  of  Tumors"  (1863-67)  3  vols.  Had 
much  to  do  with  the  canalization  and  sanitation  of  Berlin.  For 
portraits  see  Garrison,  p.  603,  Pagel,  p.  1775,  and  Werckmeister, 
1899,  3,  pi.  261. 

Vittadini,  Carlo  ( 1865).     Italian  mycologist  (Milan).     His  method 

of  distinguishing  good  silkworm  eggs  from  bad  was  published  in 
Milan  in  1859  ("Actes  de  l'Institut  Lombard,"  Tome  I). 

Voigt,  ( ■).     French  professor  in  Lyons.     Duclaux's 

friend. 

Vulpian,  Edme  Félix  Alfred  (1826-1887).  French  physician,  pathologist 
and  physiologist.  Professor  of  Pathological  Anatomy  in  Paris. 
Perpetual  Secretary  of  the  Academy  of  Sciences.  Greatly  interested 
in  rabies  inoculations.  For  portrait  see  Pop.  Sci.  Monthly,  Dec, 
1888. 

Waldeyer,  Heinrich  Wilhelm  Gottfried  (1836 ).  German  anato- 
mist, pathologist,  and  histologist.  Student  of  Henle.  Professor 
in  Strassburg  and  in  University  of  Berlin.  Director  of  the  Anatom- 
ical Institute.  One  of  the  founders  of  the  "Archiv  fur  mikros- 
kopische  Anatomie."  Member  of  various  foreign  Academies. 
For  portraits  see  Garrison,  p.  548,  and  Pagel,  p.  1806. 

Weigert,  Carl  (1845-1904).  Celebrated  German  histologist.  Assistant 
to  Waldeyer,  to  Lebert,  and  to  Cohnheim.  Professor  in  Frankfort- 
am-Main,  and  in  Leipzig.  The  first  to  stain  bacteria.  Wrote 
"Erste  Fàrbung  von  Bakterienhaufen  (1871)  and  "Fârbung  der 
Bakterien  mit  Anilinfarben  (1875).     For  portrait  see  Pagel,  p.  1826. 

Weiss,  Christian  Samuel  (1780-1856).  German  physicist,  mineralogist 
and  crystallographer.     Professor  in  Berlin. 

Willis,  Thomas  (1621-1675).  English  anatomist  and  physiologist  of 
the  brain.     For  portrait  see  Garrison,  p.  253. 

Wôhler,  Friedrich  (1800-1882).  German  physician  and  chemist. 
Studied  in  Stockholm  under  Berzelius.  Professor  in  Gôttingen. 
Fellow  of  the  Royal  Society  of  London.     Collaborated  with  Liebig. 


352  ANNOTATED    LIST   OF   PERSONS 

Studied  the  cyanides  and  benzol  compounds,  isolated  aluminium, 
beryllium  and  yttrium.  Made  many  contributions  to  science. 
Taught  many  students.  For  portraits  see  Pop.  Sci.  Monthly, 
Aug.,  1880,  and  Werckmeister,  1899,  vol.  3,  pi.  287. 

Yersin,    Alexandre    (1863 ).     French  physician  and  pathologist. 

Collaborator  of  Roux  in  the  Pasteur  Institute.  Studied  in  the 
French  colonies  where  he  discovered  the  plague  bacillus  in- 
dependently of  Kitasato. 

Youriêvitch,  Serge  ( — — ■ — •).     Attaché  of  the  Russian  legation  in 

Paris.  Eulogist  of  Duclaux  ("Bull,  de  l'Inst.  général  psycho- 
logique," 4  année,  No.  4,  1904. 


PASTEUR   IN   HIS   OLD  AGE 
(From  "Le  Centenaire  de  l'École  normal."  1895. 


INDEX 


Aerobic,  coining  of  word,  124 
life,  82 

of  anaerobic  species,  202 
Aging  of  wine,  140 
Air,  germs  in,  91,  93 
distribution  of,  101 
fewer  than  first  supposed,  103, 
191,  268 
Alcoholic  fermentation,  51,  56,  73 
Anaerobic,  coining  of  word,  124 
life,  82 

changed  structure  due  to,  200 
of  aerobic  species,  198 
Aspergillus   niger,    199 
Bail,  198,  201 
Mucor  mucedo,  198 
Mycoderma  of  wine,  201 
Pénicillium  glaucum,  199 
Anthrax,  233 
bacteridium  of,  234,  237,  245 
augmentation  of  virulence  of, 

309,  311 
diminution    of    virulence    of, 

307,  310 
preservation  of  virulence   of, 

309 
reaction    of    host,     Pasteur's 

chief  interest,  253 
return  to  virulence,   308 
spore  of,  241 

zone  of  attenuation,  305,  306 
Bert,  244,  259 
Bouley,  238 
Brauell,  233,  238 
cursed     fields     and     dangerous 

mountains,  236 
Davaine,    233,    237,    247,  248, 

250,  257 
Delafond,  235,  242 


Anthrax,  earth-worms  and,  287 
endemic  and  epidemic  nature  of, 

288 
etiology  of,  237,  242,  245,  250 
Jaillard,  238,  257,  259 
Joubert,  252 
Klebs,  uses  porous  earthen  filter, 

239 
Koch,    Robert,    241,    247,   248, 

250 
Leplat,  238,  257,  259 
Pasteur,  what  interested  him  in, 
250 
contributions    to    our   know- 
ledge of,  251,  252,  286 
PoUender,  233 
Rayer,  233 
Sanson,  238 
Signol,  238 
spore  of,  241 
Tiegel,  239 
vaccine  for,  289,  291,  292 

savings  due  to,  293 
a  virus  disease,  285 
Appert,  Emile,  IX,  X 

François,  60,  90,  143 
Arloing,  305,  315 

Aseptic  methods  advised  by  Pas- 
teur in  dressing  of  wounds,  267, 
271 
Aspartates,  20 

Aspergillus  niger,   growth  in   ab- 
sence of  air,  199 
Raulin's  culture  medium^best 
for,  225,  226 
Attenuation,  chemicals  in,  rôle  of, 
Chamberland  and  Roux  on,  306 
heat  in,  rôle   of,  Toussaint  and 
Chauveau  on,  305 


23 


353 


354 


INDEX 


Attenuation,     light    in,    rôle    of, 

Duclaux  and  Arloing  on,  305 

oxygen   in,    rôle   of,    Bert   and 

Chauveau  on,  305 
physiological  differences  between 
bacteridia   unequally   attenu- 
ated, 306,  307 
virulence  and,  304 
Autoclave,  introduction  into  bac- 
teriology, 118 

Bacillus  subtilis,  118,  242 
Bacteria,  associations  of,  rôle  of, 
264 

rôle  in  pathology,  247-249 
Bacterial       secretion       producing 

symptom    of    a    disease,    first 

example  of,  255 
Bacteriotherapy,  first  example  ^of, 

256 
Bail,  192,  198,  201 
Balard,  characterization  of,|107 
Barbet,  X,  XI 
Bastian,  101,  111,  114,  119 
Béchamp,  197 
Bêcher,  53 
Beer,  diseases  of,  188 

studies  on,  187 
Bellamy,  211 
Bellotti,  160 
Berkeley,  192 

Bernard,  Claude,  206,  209,  219,  321 
Bert,  244,  248,  259,  306 
Berthelot,  28,  137,  206,  210.  212 
Bertin,  189 
Berzelius,  28,  76,  77 
Biot,  8,  10,  11,  20 
Black,  55 
Blanchard,  280 
Bloch,  XIX 
Blood  corpuscles,  red,  comparison 

with  acetic  ferment,  127 
Bornet,  81 
Bouley,  293 
Boullay,  58 
Boussingault,  137 


Boutron,  79 
Boyle,  53 

Brauell,  233,  234,  238 
Bremer,  44 

Brewing,  Pasteur's  studies  on,  187 
Broussais,  230 
Briicke,  231 
Buffon,  87,  148 
Burdon-Sanderson,  116 
Butyric  fermentation,  79,  80,  82 
vibrio  of,  80 

CAGNiABD-Latour,  61,  64,  65,  69 

Cantani,  256 

Cantoni,  153,  157,  160 

Cellular  life,  dissymmetry  of,  28 

Chamberland,  114,  191,  226,  291, 
293  297,  306 

Chassang,  124 

Chauveau,  191,  245,  247,  248,  277 
305,  315 

Chemiotaxis,  319 

Chicken  cholera,  276 
parasite  of,  277 

Cohn,  118,  242 

Colin,  65 

Columella,  227,  229' 

Contagion,  ideas  of,  prior  to  1866, 
225 
state  of  scientific  mind  on,  in 
1876,  226 

Cornalia,  152,  160 

Corne  vin,  315 

Corpuscular  disease  of  silkworms, 
149 

Cowpox,  protection  against  small- 
pox (Jenner),  282 

Coze,  232,  274 

Culture  media,  suited  to  organisms, 
225 

Cultures,  Pasteur's  early  know- 
ledge of  how  to  make  a  series, 
252 

Crystallography,  1 

aspartates,  Pasteur's  work,  20 
Biot,  8,  10,  11,  20 


INDEX 


355 


Crystallography,  Bremer,  44 
cellular  life,  dissymmetry,  com- 
pared with,  28 
Delafosse,  5,  6,  10,  11,  12 
dissymmetry,  5 

cellular  life  and,  28 

molecular,  23 

substances    inactive    through 
loss  of,  32 
general  conclusions  on,  46 
Gernez,  separation  of  tartrates 

by  decoy,  44 
Haûy,  2,  6,  9,  10,  12 
hemihedrism,  5,  6,  13,  14 
Herschel,  10,  13 
isomorphism,  3 
Le  Bel,  37 

malates,  Pasteur's  work,  20 
Mitscherlich,  4,  13,  17 
molecular  dissymmetry,  23 
molecular     structure,     theories 

prior  to  1840,  2 
molecules,  active,  combinations 

between,  39 
paratartrates,  16 

Mitscherlich,  17 

Pasteur,  16 
Pasteur's  predecessors,  1 

work,  (See  Pastuer) 
Provostaye,  13 
right  and  left-handed  substances, 

means  of  separating,  43 
rotary  power,  depends  on  consti- 
tution of  molecule,  12 
rotation  of  plane  of  polarization, 

8,  11,  13,  14 
tartrates,  12 

Mitscherlich,  13 

Pasteur,  12 

Provostaye,  13 

Weiss,  6 

Darwin,  192,  201 

Davaine  on  anthrax,  182,  191,  232, 

233,  237,  245,  247,  248,  250,  257, 

259,  274 


Descartes,  55 

Déclat,  191 

Delafond,  235,  242,  245 

Delafosse,  5,  10,  11 

Desmazières,  61 

Dessaignes,  32,  33 

Dissymmetry,  molecular,  23 

substances  inactive  through  loss 

of,  32 
cellular  life  and,  28 
Dôbereiner,  75,  121 
Dry  sterilization,  introduction  of, 

119 
Du  Bois  Reymond,  231 
Duboué,  295 

Duclaux,  Emile,  life  of,  VII 
Madame,  VII 
Pierre-Justin,  VII 
Duclauxian  high  lights:  a  blast  of 
heat,  a  blast  of  cold,  123 
a  corner  of  the  veil  raised,  125 
a  dream  which  goes  somewhere,  84 
a  fact  is  nothing  by  itself,  213 
a  hard  necessity,  148 
a  new  world  was  opened  to  him, 

283 
a  sure  beginning  of  things,  253 
Bastian's  contribution  to  science, 

119 
Bernard,    very    respectful   with 

facts,  208 
Broussais'  cloud  of  dust,  230 
chemical       mutations      govern 

everything,  318 
chemist  to  his  finger-tips,  107 
chemistry,  physics  and  life,  272 
chemistry  in  medicine,  321 
choice  of  food  among  bacteria, 

126 
deceptiveness  of  words,  80,  227 
discoveries,     that     reveal     vast 

horizons,  303 
discussions,   mediocre  value  of, 

212 
experimental  method,  its  power, 
295 


356 


INDEX 


Duclauxian  high  lights:  faith,  in- 
tolerance of,  144 
Gay-Lussac's  coup  de  pouce,  58 
general  debility  of  intelligences, 

213 
Grand    Turk    and   Republic  of 

Venice,  130 
guess  or  be  devoured,  154 
Herschel's  drop  of  oil,  10 
historic  stumbling  stones,  1,  52, 

227 
honor  to  Davaine,  237 
how  Davaine  failed,  257,  258 
how  one  falls,  122 
how  to  understand  the  past,  227 
Jenner's  eternal  glory,  282 
judgements  revised  without  ceas- 
ing, HI 
Klebs  and  mineral  solutions,  225 
Liebig,  extractor  of  quintescence, 
75 
he    only    remained    a    little 
melancholy,  132 
life  in  struggle  with  a  compound 
endowed  with  rotary  power, 
45 
modern  surgery  full  fledged,  268 
multicolored   lanterns,    230 
obedient  to  what  mysterious  call, 

319 
old  age  and  mental  inertia,  128, 

133 
only    with    difficulty    do    great 
minds  understand  one  another, 
206 
on  pathology  in  1876,  226 
on  seeing  simply,  88,  89 
Pasteur,  a  conqueror  in  the  realm 
of  his  dream,  281 
a  pioneer,  84,  232 
man  of  large  horizons,  273 
struggling  with  error,  149 
the  apostle,  290 
twenty    years    old    in   micro- 
biology, 226 
where  he  is  without  equal,  232 


Duclauxian  high  lights:  Pasteur's 
debate  with  a  shade,  206 
dogmatic   style,   276 
first  camp  on  a  route  wherein 

he  found  immortality,  147 
good  fortune,  34 
guardian   spirit,    186 
imagination,  27,  45,  273 
iron  on  punk,  105 
Olympian  stfence,    147 
politeness    and     personal 

opinion,  208 
posthumous  writings  and  one's 

friends,  209 
Pouchet's  imagination,  93 
progress  in  science  from  change 

of  view,  7 
raging    victims,     bound    and 

howling,  294 
researches  a  la  Lavoisier,  123 
revolutionary  phrase,   71 
rôle  of  a  good  technique,  191 
slave  of  one's  education,  272 
struggle  for  existence  vs.  struggle 

for  oxygen,  256 
struggles  in  the  dark,  206 
the  enchanted  grotto,   280 
theory:  it  need  not  be  true,  it 
suffices  that  it  be  fertile,  36, 
38,  55,  111,  130 
there  are  not  on  the  palette  of 

any  painter,  285 
the   weather   vane  has  turned, 

248 
the     whipstroke    of    departure, 

218 
value  of  a  theory,  130 
Virchow's  terminology  and  sys- 
tem, 231,  232 
virulence  is  a  state  of  perpetual 
becoming,  311 
sums  up  the  result  of  conflict, 
308 
vital  force,  231,  300,  301 
we  have   not  the  same  sort  of 
brain,  106 


INDEX 


357 


Duclauxian     high     lights:     what 
secret  instinct,  what  spirit  of 
divination,  289 
why  turn  the  carpet  to  see  the 
design?,  88 

Du  jar  din,  80 

Dumas,  58,  87,  107,  145,  148,  154 

Dusch,  91,  94,  101 

Duval,  197 

Ehrenberg,  80 

Epidemics,  Pasteur  on  suppres- 
sion of,  173,  223,  224 

Eremacausis,  121 

Erysipelas  of  the  pig,  310 

Etiology  of  microbial  diseases, 
studies  on,  225 

Fabroni,  60 
Feltz,  232,  274 
Fermentation,  51 
aerobic  and  anaerobic  life  of,  79, 

82,  205 
alcoholic,  73 

and  spontaneous  generation,  85 
Appert,  preserving  methods  of, 

60 
balance    in     chemistry,     intro- 
duction of,  56 
Bêcher,  53 
Bernard,  206 
Berzelius,  76,  77 
Boullay,  58 
Boutron,  79 
Boyle,  53 

Cagniard-Latour,  61,  64,  65 
cause  of,    theory    as  to,   Gay- 
Lussac's,  218 
Liebig's,  218 
Pasteur's,  205,  218 
Colin's  work,  65 
disease,      association     between 
phenomena    of    fermentation 
and,  53 
Dôbereiner,  75 
Dujardin,  80 


Fermentation,  Dumas,  58 
Ehrenberg,  80 
Fabroni,  60 
Frémy,  79,  213 
Gay-Lussac,  57,  58,  59,  62 
Helmholtz,  63,  64,  84 
knowledge  of,  before  Lavoisier, 

51 
lactic,  67,  79 
Lavoisier,  55,  56,  57,  58 
Lièbig,  54,  64,  68,  69,  75,  76,  80, 

130 
Mitscherlich,  65 
oxygen,  rôle  of,  in,  61 
Paracelsus,  53 

Pasteur,    discussion    with    Ber- 
nard, 206 
lactic  fermentation,  67 
Quevenne,  65 
Schwann,  61,  62,  63,  65 
specificity  of,  71 
Stahl,  54,  55,  66 
Thénard,  57,  59,  61,  65,  74,  78 
Turpin,  65 
Van  Helmont,  53,  55 
Willis,  54,  66 

yeast,  rôle  of,  in,  Berzelius,  76 
Gay-Lussac,  60 
Helmholtz,  63 
Liebig,  64 
Pasteur,  73,  74,75 
Schwann,  62 
Fermenting  power  of  Mycoderma 

aceti,  125 
Flacherie,  173 
Flaming       glassware,       Pasteur's 

method  of,  119 
Fracastoro,  229 
Fraenkel,  304 
Frémy,  79,  111,  213 
Frey,  152 

Gay-Lussac,  57,  58,  59,  62,"  90,  91, 

102,  119,  218  jfg 

Germination  in  absence  of^air,  264 
Germs  in  air,  91,  93 


358 


INDEX 


Germs  in  air,  distribution  of,  101 
not     everywhere     abundant, 
103,  191,  268 
reaction  to  acid  liquids,  117 
rejuvenescence  of,  air  necessary 
for,  118 
Gernez,  44,  166 
Gibier,  272 
Grancher,  299 
Guérin,  Alphonse,  191 
Guérin,  Jules,  104 
Guérin- Mène  ville,  152 
Guyon,  191 

Hales,  55 

Hallier,  192 

Hameau,  229,  230 

Hatty,  2,  6,  9,  10 

Helmholtz,  63,  64,  84,  92,  101,  231 

Henle,  228,  230 

Herschel,  10,  13,  35 

Heterochronia,  231 

Heterotopy,  231 

Hoffmann,  192,  197 

Immunity,  313 
cellular  theory  of,  317 
chemical  and  humoral  theories 

of,  312 
problem  of,  299 
relative,  278 

Jaillard,  238,  257,  259,  261 
Jenner,  232,  275,  282 
Joly,  106,  118 

Joubert,  associated  with  Pasteur, 
114,  116,  191,  226,  252 

Klebs,  225,  239,  248 

Koch,   Robert,   adverse  criticisms 

of,  293 
distinguished  contributions  of, 

226,  242,  245,  247,  248,  250, 

286 
Kutzing,  61 


Lackerbatjer,  165 

Lactic  fermentation,  67,  79 

Lannelongue,  270 

Lavoisier,  55-59 

Le  Bel,  37 

Lebert,  152 

Lechartier,  211 

Lefèvre,  55 

Lèmery,  55 

Leplat,  238,  257,  259,  261 

Leuwenhoeck,  61 

Liebig,  54,  64,  65,  66,  68,  69,  75,  76, 

80,  121,  122,  128,  134,  206,  218, 

231 
Linnaeus,  230 
Lister,  104,  191,  269 
Loffler,  adverse  criticisms  of,  293 
Ludwig,  231 

Malates,  20 

Metastatic  abscesses,  266 

Metchnikoff,  317,  318,  319 

Microbial  diseases  and  virus  dis- 
eases, 273 

Microbial  pathology,  great  teach- 
ings of,  in  Pasteur's  book  on 
silkworms,  182 

Milk,  sterilization  of,  101 

Mitscherlich,  4,  13,  17,  65 

Moitrel  d'Élément,  55 

Molecular  dissymmetry  of  tartra- 
tes, 23 
relation  to  nutritive  character,  46 

Molecular  structure,  theories  prior 
to  1840,  2 

Molecules,  active,  combinations 
between,  39 

Molière,  90 

Morts-flats,  164,  173 

Mucor  mucedo,  anaerobic  life  of, 
198,  200 

Mttntz,  212 

Musset,  106,  118 

Mycoderma  aceti,  124 

supposed    transformation    of, 
197  . 


INDEX 


359 


Mycoderma  vini,  growth  in  absence 
of  air,  201 
supposed  transformation  into 
an  alcoholic  ferment,    192, 
197 

Needham,  89,  90 

Obermeier,  249 

Organized      ferments,      Pasteur's 

theory,  69,  78,  79 
Osimo,  153,  157,  160 
Oxidation  in  contact  with  air,  121 
Oxygen,  rôle  of,  in  fermentation, 
61,  123,  125,  205 

toxic  rôle  of,  306 

Paracelsus,  53,  229 

Parasite,  reaction  of  host,  Pasteur's 

interest  in,  254 
Paratartrates,  16 

Pasteur,  aerobic  and  anaerobic  life, 
discovery  of,  79,  82 
aerobic  life  of  anaerobic  species, 

202 
alcoholic  fermentation,  73 
anaerobic  life  of  aerobic  species, 

198 
anthrax,  endemic  and  epidemic 
nature  of,  287 
etiology  of,  contributions  to, 

245,  251,  252,  286 
vaccine  for,  289-293 
virus  disease,  289 
aseptic     methods     of     dressing 
wounds    advocated   by,    267, 
271 
antiseptics,  effect  of,  first  hint,  71 
aspartates,  work  on,  20,  32,  37, 

38 
atomic  groupings,   contribution 

to  our  knowledge  of,  22 
bacteria,    associations    of,    rôle, 

264 
bacterial  species,  conception  of 
action  of,  in  disease,  301 


Pasteur,  Bastian,  discussion  with, 

114 
beer,  studies  on,  187 
Bernard,    discussion    with,    on 

fermentation,  206 
boil  of  the  bone,  270 
brewing,  studies  on,  187 
butryic  fermentation,  79,  81,  82 

vibrio  of,  80 
chicken  cholera,  276 
combinations     between     active 

molecules     of     rotary     sub- 
stances, 40 
crystallography,  1 
culture    media,    importance    of 

suitable,  76,  225 

influence  of  acid  and  alkalies 

on,  71 
discouraged,  174 
discovers  motile  bacteria,  80 
disregard  of  morphology,  254 
dissymmetrical  molecule,   three 

dimensional,  37 
dissymmetry  of  cellular  life,  28 
equipment,  93 
erysipelas  of  the  pig,  studies  of, 

310 
etiology   of   microbial   diseases, 

studies  on,  225 
fermentation,  cause  of,  218 

physiological    theory    of,    85, 
205 
Frémy,   discussion  with,    111 
germs  in  air,  93,  103 
germ-specificity,  192 
groping,  115,  159,  163,  164,  166, 

167 
heating  of  wines,  141 
Henle  and,  229 

illusions  of  an  experimenter,  280 
immunity,  278,  279 

cellular  theory  of,  317 

chemical  and  humoral  theories 
of,  312,  316 

problem    of,    strife    between 
cells,  300 


360 


INDEX 


Pasteur,   indifferent  to  perfection 
of  technique,  191 
insight,  19,  32,  222,  254,  270,  271, 

287 
Institute,  299 
lactic  fermentation,  67,  79 
Liebig,  discussion  with,  128 
malates,  work  on,  20,  33,  38 
masterful  qualities,  72,  74,  178 
microbial    and    virus    diseases, 

discovery  of  identity,  281 
microscopical   studies,    258 
milk,  sterilization  of,  101 
molecular  dissymmetry  and  ro- 
tary power,  correlation  of,  36 
not  a  naturalist,  81 
on  human  plagues,  223,  224 
opinion   on   danger   of   precon- 
ceived ideas,  193 
organized  ferments,  69,  79 
osteomyelitis,  270 
oxidation  in  air,  122 
oxygen,  rôle  of,  in  disease,  264 
parasite,    reaction    of    host    to, 

254 
paratartrates,  work  on,  16 
pathological    conflicts,    269 
Pouchet,  Joly  and  Musset,  dis- 
cussion with,  105 
puerperal  fever,  270 
rabies,  294 

cultures  of,  in  the  living  organ- 
ism ,296 
prophylaxis,  298 
rotary  sub  tances,  right  and  left- 
handed,  means  of  separating,  43 
septic  vibrio,  259 
silkworms,    and    human    path- 
ology, 173,  182,  186 
corpuscular  disease  (pébrine), 

149 
morts-flats  (flacherie),  164, 173 
studies  on  diseases  of,  145 
species,    transformation   of   one 

into  another,  190,  192 
spontaneous  generation,  93,  119 


Pasteur,  spores,  of  butyric  vibrios, 
241 
rôle  of,  244 
staphylococcus,  discovery  of,  269 
struggle   for   existence,    concep- 
tion of,  301,  317 
susceptibility  to  infection,  indi- 
vidual variation  in,  181 
tartrates,  work  on,  12,  16,  30,  36 
technique,  226 

temperature,  relation  of,  to  in- 
fection, 271 
There,   there  is  its  picture!  271 
toxines,  discovery  of,  255 
training  in  1870,  186 
transformation  of  species,  192 
vaccines,  discovery  of,  280,  281 
vinegar-making,  phenomena  of, 

122 
virulence,  and  attenuation,  304 
variations  in,  attributed  first 
to  several  organisms,  274 
virus,  attenuation  of,  discovery 
of,  302 
-diseases    and    microbial  dis- 
eases, the  same,  281 
water,  contaminating  germs  in, 

116 
wine,  action  of  oxygen  on,  136 

diseases  of,  134 
yeast  of  wine,  134,  214,  217 
Pathology,  Pasteur's  entrance  into 

field  of,  145 
Pébrine,  149 

origin  of  name,  152 
Péligot,  166 

Pénicillium    glaucum,    growth    in 
absence  of  air,  199 
supposed    transformation    of 
yeast  into,  192 
Pfeffer,  46 
Pfeiffer,  319 
Phagocytosis,  317 
Philippi,  152,  160 
Phylloxera,  143 
Pollender,  233 


INDEX 


361 


Pouchet,  93,  105,  118,  119 
Predecessors  of  Paateur  in  crystal- 
lography, 1 
Provostaye,  13 
Puerperal  fever,  270 
Pus  vibrio,  265 

QtJATREFAGES,   152,   154 

Quevenne,  65 

Rabenhorst,  81 

Rabies,  294 

Chamberland,  297 
cultures  in  living  host,  296 
Duboué's  discovery,  295 
prophylaxis,  298 
Roux,  297 
Thuillier,  297 

virus  diseases,  analogies,  298 
preservation  of  virulence  of, 
309 

Raulin,  225 

Rayer,  233,  235 

Recklinghausen,  249,  250 

Redi,  86 

Right  and  left-handed  rotary  sub- 
stances, means  of  separating,  43 

Rindfleisch,  249 

Rossignol,  291 

Rotary  power,  depends  on  shape 
of  molecule,  12 

Rotation  of  plane  of  polarization,  8, 
11,  13,  14 

Roux,  191,  226,  297,  306 

Sainte-Claire- Deville,  28 
Sanderson,    See  Burdon-Sanderson 
Sanson,  238 
Schroeder,  91,  94,  101 
Schultze,  90,  92 
Schutzembach,  122 
Schwann,  61-65,  91,  95,  100 
Sédillot,  268 
Septic  vibrio,  257 

effect  of  air  on,  265 


Septicemia,  260 
Signol,  238,  259 
Silkworms,  diseases  of,  145 

digestive    tract    full    of    mi- 
crobes, 180 
flacherie  of,  164,  173 
contagious  nature  of,  184 
distribution    of    germs    in, 

widespread,  182 
hereditary  character  of,  176 
life  history  of,  149 
morts-flats,     See  flacherie 
pébrine  (corpuscular  disease), 
149 
Bellotti,  160 
Cantooi,  153,  157,  160 
cause  of,  162,  170 
contagious  nature  of,  171. 
Cornalia,  152,  160 
Frey,  152 

Gernez,  159,  166,  167,  169 
Guérin-Mèneville,  152 
hereditary  nature  of,  171 
Lebert,  152 
Osimo,  153,  157,  160 
Péligot,  166 
Philippi,  152,  160 
Quatrefages,  152,  154 
Susani,  173 
Vittadini,  153,  160 
teachings  of  microbial  patho- 
logy in   Pasteur's  volumes 
on,  182 
Spallanzani,  89,  91,  92,  95,  96 
Species,  transformation  of  one  into 
another,  190,  197,  201 
Bail,  192 
Béchamp,  197 
Berkeley,  192 
Duval,  197 
Hallier,  192 

Hoffmann,    192,  197,  201 
Mycoderma    aceti,    197 
Mycoderma  vini,  194,  197 
Trécul,  192,  197 
Turpin,  192,  201 


362 


INDEX 


Spontaneous  generations,  85 

and  fermentation,  85 

Balard,  107,  109 

Bastian,   101,   111,    114,    116, 
119 

Buffon,  87 

Burdon-Sanderson,  116 

Chamberland,  114,  116 

Cohn,  118 

Dumas,  107,  108,  109 

Dusch,  91,  94,  101 

Frémy,  111 

Gay-Lussac,  90,  91,  92,   102, 
118,  119 

Helmholtz,  92,  101 

in  decoction  of  hay,  110 

in  heated  urine,  115 

Joly,  106,  109,  118 

Joubert,  114 

Musset,  106,  109,  118 

Needham,  89 

Pasteur,  93 

Pouchet,   93,    105,    106,    109, 
115,  118,  119 

Schroeder,  91,  94,  101 

Schultze,  90,  91,  92 

Schwann,  91,  95,  100 

Spallanzani,  89,  92,  95,  96 

Tyndall,  92,  105 
Spore,  conception  of,  117,  118 
rôle   of,    in   anthrax,    241,   261, 

264 
vitality  of,  286,  289 
Stahl,  54,  55,  66 

Staphylococcus,  discovery  of,  269 
Struggle  for  existence,  317 

idea   introduced   into   patho- 
logy, 256 
Susani,  173 

Susceptibility  to  infection,  indivi- 
dual variation  in,  181 

Talamon,  304 
Tartrates,  12 
hemihedrism  and  rotary  power 
in,  16 


Temperature,  relation  of,  to  infec- 
tion, 271 

Thénard,  57,  59,  61,  65,  74,  78 

Theory  of  fermentation,  Pasteur's, 
205 

Thomas,  315 

Thuillier,  297,  299,  310 

Thuret,  81 

Tiegel,  239 

Toussaint,  305 

Toxines,  discovery  of,  255 

Trécul,  192,  197 

Turpin,  65,  192,  201 

Tyndall,  92,  105 

Vaccines,  and  viruses,  study  of,  273 

discovery  of,  280 
Van  Helmont,  53,  55 
Van-t-Hoff,  37 
Varro,  227,  229 
de  Vergnette-Lamotte,  144 
Vinegar,  manufacture  of,  121 
German  process,  122,  127 
Liebig,  122,  128 
Orleans  process,  123 
Pasteur,  122,  132 
mycoderma  of,  124,  137 
Virchow,  230,  232,  301 
Virulence,    augmentation  of,   310, 
311 
definition  of,  308,  311 
preservation  of,  309 
return  to,  308 

variations  in,  273,  297.  307 
Virulence,  and  attenuation,  304 
Virus,  247,  252 
attenuation    of,    Pasteur's    dis- 
covery of,  302 
-diseases  and  microbial  diseases, 

273 
versus  parasite,  245,  250,  252 
Viruses    and    vaccines,  study  of, 

273 
Vital  phenomenon  versus  molecu- 
lar disintegration,  130 
Vittadini,  153,  160 


INDEX 


363 


Voigt,  XIV 
Vulpian,  299 

Waldeyeb,  249 

Water,  distribution  of  bacteria  in, 

116 
Weigert,  great  service  of,  250 
Weiss,  6 
Willis,  54,  66 

Wine,  action  of  oxygen  on,  136 
Berthelot,  137 
Boussingault,  137 
Pasteur,  136 
aging  of,  140 
diseases  of,  133 
Liebig,  133,  134 
Pasteur,  134,  135 
mycoderma  of,  138,  192,  197, 
201 


Wine,  heating  of,  141 
Wines  and  vinegars,  121 
Wôhler,  28 

Yeast,   rôle  in  fermentation,   60, 
62,  65,  73 
Berzelius,  76 
Dôbereiner,  75 
Helmholtz,  63 
Liebig,  64 
Pasteur,  73,  75 
Schwann,  62 
of  beer,  aerobic  life  of,  202 
of  wine,  134,  135,  217 

origin  of,  214 
supposed    transformation    into 
other  organisms,  192,  197 
Yersin,  XVIII 
Youriévitch,  "V 


v  VU      X    "       ls7C\ 


>fc$t 


COLUMBIA   UNIVERSITY   LIBRARIES 
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the  Librarian  in  charge. 


DATE   BORROWED 

DATE   DUE 

DATE   BORROWED 

DATE    DUE 

JUN  2  6 

1941 . 

' 

1  !a^P. 

m  ?    i 

C28(546) M25 

